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colocation location order 의미

GrooveYOU 2017. 2. 10. 15:37

2017. 2. 10. 15:37

http://linux-ha.osdn.jp/wp/archives/3868

변경 내역

2013.9.19 초판 제정
2016.3.24 Pacemaker-1.1에 대응

Contents [ hide ]

■ 소개

Linux-HA Japan을 보시는 여러분 안녕하세요. Linux-HA Japan 속 사람 동쪽라고합니다 m (_ _) m

"움직여 이해 Pacemaker - CRM 설정 편 ~ 그 3」라고하는 것으로, 전전번 , 전회 의 계속입니다.

이번의 예제 설정 파일 을 제어하는 다음 7 항목을 모두 해독 할 수 있습니다. 3 회에 걸친 CRM 설정 편은 이번이 마지막입니다.

1. STONITH은 무효입니다. ( 그 1 에서 읽어 내고 있음)
2. 1 회 자원 고장 F / O합니다. 자동 장애 복구는하지 않습니다. ( 그 1 에서 읽어 내고 있음)
3. resource1, resource2라는 자원을 grp라는 group (그룹)합니다. ( 2 에서 읽어 내고 있음)
4. resource3라는 자원을 clnResource라는 clone (복제) 자원으로 두 시스템에서 시작합니다. ( 2 에서 읽어 내고 있음)
5. resource1,2,3 자원은 반드시 resource3 (clnResource) → resource1 → resource2 순으로 시작합니다. (일부 2 에서 읽어 내고 있음)
6. grp는 둘 중 하나의 머신에서 시작합니다. 두 컴퓨터가 실행 가능한 상태의 경우 pm01을 우선합니다.
7. resource3 (clnResource)가 시작되지 않은 노드에서 resource1 및 resource2 (grp)가 시작되지 않습니다.

※ 전회, 전전번의 기사에서 자원 이름을 CRM 구성과는 다른 "dummy1」등이라고 기재되어 있었지만,"resource1 "오류였습니다. 죄송합니다.

이번 주목하는 것은 다음 부분입니다.

### Resource Location ###
location rsc_location-1 grp \
    rule 200: #uname eq pm01 \
    rule 100: #uname eq pm02

### Resource Colocation ###
colocation rsc_colocation-1 INFINITY: grp clnResource

### Resource Order ###
order rsc_order-1 0: clnResource grp symmetrical=false

이 곳에서는 location, colocation, order 세 가지 명령을 사용합니다.

이 3 개는 모두 자원에 대해 " 제약 "을 설정하는 명령입니다.

「제약」을 사용하면 자원이 시작할 때 다음 세 가지 조건을 설정할 수 있으며, 각 명령에 대응하고 있습니다.

location → 위치 : 모든 노드에서 시작 하는가?
colocation → 동거 : 어떤 자원과 함께 시작 하는가?
order → 순서 : 어떤 자원의 전 / 후 시작할지?

조속히이 3 명령의 설명을 말하고 싶지만 그 전에 제약을 이해하는 데 중요한 개념이 있습니다.
그것은 " 점수 값 "입니다.

자세한 내용은 나중에 설명하지만 제약의 3 명령은 모두있는 규칙에 점수 값을 설정하는 것입니다.
그래서 우선 점수 값의 설명에서하고 싶습니다.

■ 점수 값의 큰 노드에서 자원 시작

점수 값은 자원을 모든 노드에서 시작하거나 우선 순위를 나타내는 값입니다.
노드를 시작하거나 리소스를 추가하거나 고장이 발생하거나와 클러스터의 상태에 변화가있을 경우 Pacemaker가 자동으로 (재) 계산합니다.

Pacemaker는 산출 한 점수 값을 비교하여 가장 큰 값의 노드에서 자원을 시작합니다.
산출 한 점수 값이 음수 경우 해당 노드에서 자원을 시작할 수 없습니다.

점수 값은 다음 범위 중 하나입니다.

-INFINITY <음수 <0 <양수 <INFINITY

"-INFINITY (마이너스 무한대)」와 「INFINITY (무한) '는 특별한 값으로, 전자는"금지 ", 후자는"강제 "를 나타냅니다.
각각 다른 값의 연산 결과는 다음과 같이 정의되어 있습니다 .

다른 값 + INFINITY = INFINITY
다른 값 - INFINITY = -INFINITY
INFINITY - INFINITY = -INFINITY

1,2 번째 연산 결과는 어딘지 모르게 압니다 만, 3 번째의 연산 결과는 조금 이상한 생각이 듭니다.
수학적으로 말하면 ∞-∞는 부정입니다. 이 클러스터 리소스를 시작할지 여부가 불확실한 와서는 불편합니다.
-INIFNITY는 일반적으로 고장이 발생한 노드에 부여됩니다. 만약 INIFINITY - INFINITY이 부정이라면 아래의 제약 명령 INFINITY를 부여한 노드에서 장애가 발생하면 자원이 시작할지 여부가 부정되어 버립니다.
이것을 피하고 고장난 노드에서 시작되지 판단하는 -INFINITY을 우선하고있는 것입니다.

점수 값은 기본적으로 Pacemaker가 클러스터의 상황에 따라 자동으로 산출되지만, 후술의 「제약」에 의해 특정에 경우의 점수 값을 사용자가 결정 (Pacemaker에 제공) 할 수 있습니다.
「제약」을 능숙하게 활용 점수 값을 조작하는 것으로, 자원의 시작을 사용자 마음대로 조종 할 수있는 것입니다.

■ location에서 시작 노드를 제약

location은 시작 노드를 제약하는 명령입니다.
그 노드의 상태를 평가하고 그것에 매치했을 경우의 점수 값을 정의하여 설정합니다.

location의 개요 대표적인 형식은 다음과 같습니다.

요약	논리 연산 식을 만족하는 경우의 점수 값을 지정하여 자원을 시작할 노드를 제한합니다. 논리 연산 식에서는 주로 "노드 이름"과 "속성 값"을 평가할 수 있습니다. rule ~ 행을 여러 작성하여 1 리소스에 여러 평가 식 및 점수를 설정할 수 있습니다.
서식	location <제약의 ID> <리소스 ID> \ rule <점수 값> : <노드 상태 평가 식> and \| or <노드 상태 평가 식> ...] [\] [rule ...]
설정 항목	제약의 ID	이 제약을 고유하게 식별하는 ID를 부여합니다. 영숫자 클러스터에서 고유 한 임의의 문자열을 지정합니다.
	리소스 ID	제약의 대상이되는 자원을 자원 ID로 지정합니다. rule ~ 행을 여러 작성하여 1 리소스에 여러 점수 값을 설정할 수 있습니다.
	점수 값	오른쪽의 논리 연산식이 참이면 점수 값을 지정합니다.
	노드 상태 평가 식	노드 상태의 평가 식은 주로 "노드 이름의 평가"와 "속성 값의 평가」「속성 값의 유무」의 3 패턴을 자주 사용합니다 ※. 기법은 각각 다음과 같은 형태입니다. #uname <연산자> <값> 노드 이름과 <값>을 <연산자>에서 비교 · 평가합니다. "#uname」라고하는 기술은 해당 노드의 노드 이름에 전개되고 평가됩니다. <값>은 임의의 숫자를 비교 대상으로 지정할 수 있습니다. <속성 값 이름> <연산자> <값> <속성 값 이름>으로 지정한 속성 값과 <값>을 <연산자>에서 비교 · 평가합니다. <값>은 임의의 숫자를 비교 대상으로 지정할 수 있습니다. defined \| not_defined <속성 값 이름> <속성 값 이름>으로 지정한 속성 값이 정의되어 있는지 여부를 평가합니다. defined은 해당 속성 값이 정의되어있을 때 진정한, not_defined은 정의되어 있지 않을 때 진정한입니다. ※ 날짜도 평가할 수 있지만, 여기에서는 설명을 생략합니다. 알고 싶은 분은 CRM-CLI 공식 설명서 (일본어 버전) 참조하십시오. <연산자> 에는 다음을 사용할 수 있습니다. lt : 왼쪽이 오른쪽보다 작은 경우에 true를 만든다 gt : 왼쪽이 오른쪽보다 크면 참이된다 lte : 왼쪽이 오른쪽보다 작거나 같으면 참이된다 gte : 왼쪽이 오른쪽보다 크거나 같으면 true를 만든다 eq : 왼쪽과 오른쪽이 동일한 경우에 true를 만든다 ne : 왼쪽과 오른쪽이 같지 않으면 true를 만든다 또한, and와 or를 사용하여 여러 논리 연산 식의 결과를 통합 할 수 있습니다.

평가 식에서 등장하는 속성 값 은 Pacemaker가 보유하고있는 값으로 노드마다 자원의 상태와 클러스터의 상태를 나타냅니다.
상황에 따라 값이 변화하면 그 노드의 상태를 알 수 있습니다.
일반적으로 자원 에이전트가 자원의 실시간 상태를 나타내는 데 사용합니다.
예를 들어 네트워크 소통을 확인하는 자원 (ocf : pacemaker : pingd)는 네트워크가 소통하는 경우 지정한 속성 값에 값을 추가하고 소통하지 않으면 값을 뺍니다. 속성 값은 모니터마다 실시간으로 변화하기 때문에이 속성 값을 살펴보면, 지금 현재 네트워크가 소통하고 있는지를 확인할 수 있도록되어 있습니다.

또한 crm_mon 명령에 -A 옵션을 쓰면 속성 값을 표시 할 수 있습니다.

다음 부분은 그룹 grp에 대해 노드 pm01의 시작은 점수 200 노드 pm02의 시작은 점수 100을 지정합니다.
즉, grp의 시작 노드로 pm01을 우선하도록 제한하고 있습니다.

location rsc_location-1 grp \
    rule 200: #uname eq pm01 \
    rule 100: #uname eq pm02

이제 다음이 読み解け했습니다.

6. grp는 둘 중 하나의 머신에서 시작합니다. 두 컴퓨터가 실행 가능한 상태의 경우 pm01을 우선합니다.

■ colocation에서 동거하는 자원을 제약

colocation는 지정된 (여러) 자원이 동일 노드에서 시작하는 것에 대해 점수 값을 설정합니다.

colocation의 개요 대표적인 형식은 다음과 같습니다.

요약	자원과 다른 자원이 동일한 노드에 존재하는 것에 대해 점수 값을 설정합니다.
서식	colocation <제약의 ID> <점수 값> : <리소스 ID> : <역할> <리소스 ID> : <역할>] [<리소스 ID> : <역할>]] ...
설정 항목	제약의 ID	이 제약을 고유하게 식별하는 ID를 부여합니다. 영숫자 클러스터에서 고유 한 임의의 문자열을 지정합니다.
	점수 값	오른쪽에 기술 한 자원을 동거하는 것에 대한 점수 값을 지정합니다. 일반적으로 INFINITY를 지정 동거를 강제 또는 -INFINITY을 지정 다른 노드에서 시작을 강제합니다.
	리소스 ID	제약의 대상이되는 자원을 자원 ID로 지정합니다. 왼쪽의 자원 시작할 때 오른쪽 자원이 동일한 노드에 존재하는 것에 대해 점수 값을 설정합니다. 리소스 ID를 기술하는 순서에 의미가 약간 변경에 유의하십시오. 또한 ": <역할>"와 롤을 작성할 수 있습니다. 롤은 ms 명령으로 자원을 정의 할 때 필요한 개념입니다. Master와 Slave 등의 자원 상태를 말합니다. ms 명령은 이번 기사에서는 대상으로하고 있지 않기 때문에 자세한 설명은 생략합니다.

다음 부분은 그룹 grp의 시작시 clnResource가 동일한 노드에서 시작하는 (하고있는) 것을 강제하고 있습니다.

colocation rsc_colocation-1 INFINITY: grp clnResource

이제 다음이 読み解け했습니다.

7. resource3 (clnResource)가 시작되지 않은 노드에서 resource1 및 resource2 (grp)가 시작되지 않습니다.

■ order 순서를 제약

order는 지정된 (여러) 자원의 액션을 실시하는 순서 에 대해 점수 값을 설정합니다.

order의 개요 대표적인 형식은 다음과 같습니다.

요약	지정된 (여러) 자원의 액션을 실시하는 순서에 대해 점수 값을 설정합니다. 액션은 시작, 승격 등이 포함됩니다.
서식	order <제약의 ID> <점수 값> : <리소스 ID> : <액션> <리소스 ID> : <액션>] ... [symmetrical = true \| false]
설정 항목	제약의 ID	이 제약을 고유하게 식별하는 ID를 부여합니다. 영숫자 클러스터에서 고유 한 임의의 문자열을 지정합니다.
	점수 값	이 제약에 대한 점수 값을 지정합니다. 0보다 큰 값을 지정하면 왼쪽의 자원이 상태 변화하면 오른쪽의 리소스에 영향 (중지하거나 시작 실행)합니다 ( Mandatory Ordering ). 0을 지정하면 왼쪽 자원의 액션 실행시 이외의 상태 변화가 오른쪽 자원에 영향을주지 않습니다. ( Advisory Ordering ) 조금 어려운 표현되었습니다 만, 0과 INFINITY를 설정 한 경우 다음과 같은 이미지가된다고 이해하면 좋을 것입니다. 0 : 가급적 왼쪽 → 오른쪽으로 <액션>하기 INFINITY : 절대 왼쪽 → 오른쪽으로 <액션>해야한다
	리소스 ID	제약의 대상이되는 자원을 자원 ID로 지정합니다. 왼쪽의 자원 시작할 때 오른쪽 자원이 동일한 노드에 존재하는 것에 대해 점수 값을 설정합니다. 리소스 ID를 기술하는 순서에 의미가 약간 변경에 유의하십시오.
	액션	액션은 대상이되는 자원을 시작 (start), 정지 (stop) 상승 (promote) 강등 (demote) 중 어느 것을 실행시 제한 여부를 지정합니다. 지정하지 않으면 기본값은 start입니다. ※ 승격 (promote) 및 강등 (demote)은 ms 명령으로 자원을 정의 할 때 필요한 개념입니다. ms 명령은 이번 기사에서는 대상으로하고 있지 않기 때문에 자세한 설명은 생략합니다.
	symmetrical	symmetrical이 제한 역순 제약을 자동으로 설정할지 여부를 true (=) 또는 false (= 안)에서 지정합니다. 예를 들어, "시작 A → B의 순서로 수행"이라는 제약에 대해 "정지는 B → A 순으로 진행할 것"이라고 반대의 제약을 자동으로 설정할 수 있습니다. 지정하지 않으면 기본값은 true입니다.

다음 부분은 clnResource → grp의 순서로 시작하는 것을 보여줍니다.
점수 값은 0이므로 시작 후 clnResource의 상태 변화는 grp에 영향을주지 않습니다.
symmetrical을 false로하고 있기 때문에 정지 순서는 부정입니다.

### Resource Order ###
order rsc_order-1 0: clnResource grp symmetrical=false

이제 다음이 読み解け했습니다.

5. resource1,2,3 자원은 반드시 resource3 (clnResource) → resource1 → resource2 순으로 시작합니다.

염려되는 분도 있을지도 모릅니다 만, 전회 소개 한 group 명령도 동거과 순서를 지정하는 것이 었습니다.
예를 들어, "group grp1 resource1 resource2"는 "resource1과 2는 반드시 동거」, 「resource1 → resource2의 순서로 시작"을 정의합니다.

group은 colocation과 order를 조합하여 재현 할 수 있습니다.

다음 페이지에서 이번 찾은 것을 응용 한 실험을 해 봅시다.

■ 실험 1 colocation 점수 값을 -INFINITY에 보면

먼저 예의 CRM 설정 에서 Pacemaker를 시작합니다.
다음과 같이 시작해야합니다.

# crm_mon -rfA
～略～

Online: [ pm01 pm02 ]

Full list of resources:

Resource Group: grp
    resource1 (ocf::heartbeat:Dummy): Started pm01
    resource2 (ocf::heartbeat:Dummy): Started pm01
Clone Set: clnResource
    Started: [ pm01 pm02 ]

Node Attributes:
* Node pm01:
    + pm02-eth1 : up
    + pm02-eth2 : up
* Node pm02:
    + pm01-eth1 : up
    + pm01-eth2 : up

Migration summary:
* Node pm01:
* Node pm02:

다음 클러스터를 가동시킨 채로 다음 명령 colocation 점수 값을 -INFINITY에 다시 씁니다.
두 노드에서 실행해도 괜찮습니다.

# crm configure edit
→vi等のエディタが起動し、現在のCRM設定が編集可能になる。
　以下部分の「inf」を「-inf」に書き換える。

    colocation rsc_colocation-1 inf: grp clnResource
      ↓書き換え
    colocation rsc_colocation-1 -inf: grp clnResource

　書き換えたらエディタを保存終了する。(viの場合、Esc→:wq)

변경은 즉시 Pacemaker에 반영되어 아마 다음과 같이됩니다.

# crm_mon -rfA
～略～

Online: [ pm01 pm02 ]

Full list of resources:

 Resource Group: grp
     resource1  (ocf::heartbeat:Dummy): Stopped ★
     resource2  (ocf::heartbeat:Dummy): Stopped ★
 Clone Set: clnResource
     Started: [ pm01 pm02 ]

Node Attributes:
* Node pm01:
    + pm02-eth1                         : up
    + pm02-eth2                         : up
* Node pm02:
    + pm01-eth1                         : up
    + pm01-eth2                         : up

Migration summary:
* Node pm01:
* Node pm02:

★ 부분에서 resource1,2이 정지되었음을 알 수 있습니다.

이것은 grp (= resource1,2)와 clnResource (= resource3)의 colocation 점수 값을 -INFINITY에 다시 쓴 것으로,
제약 "grp과 clnResource 절대로 다른 노드에서 시작한다 '는 의미 되었기 때문에 입니다.
clnResource는 복제를위한 두 노드에서 시작하고 그대로는이 제약을 지킬 수 없기 때문에 grp을 중단 할 수밖에 없었습니다.

이 상태에서 clnResource을 중지하면 어떻게 될까요?
다음 명령을 실행하십시오. 두 노드에서 실행해도 괜찮습니다.

# crm resource stop resource3

아마 다음과 같이되었다고 생각합니다.

# crm_mon -rfA
～略～
Online: [ pm01 pm02 ]

Full list of resources:

 Resource Group: grp
     resource1  (ocf::heartbeat:Dummy): Started pm01 ★
     resource2  (ocf::heartbeat:Dummy): Started pm01 ★
 Clone Set: clnResource
     Stopped: [ resource3:0 resource3:1 ] ☆

Node Attributes:
* Node pm01:
    + pm02-eth1                         : up
    + pm02-eth2                         : up
* Node pm02:
    + pm01-eth1                         : up
    + pm01-eth2                         : up

Migration summary:
* Node pm01:
* Node pm02:

☆ 부분에서 clnResource (resource3)가 정지하고 ★ 부분에서 정지했다 resource1,2가 시작되었는지 알 수 있습니다.

clnResource를 수동으로 중지함으로써 colocation 제약으로 억제되어 있던 resource1,2가 부팅 가능하게 된 것입니다.

■ 실험 2 order 점수 값을 INFINITY에 보면

order 점수 값에 0과 INFINITY를 설정하고 0과 INIFINITY의 의미의 차이를 확인합니다.

CRM 구성은 3 개의 Dummy 자원을 order에서 순서 제약을 건 그냥 단순한 것을 사용합니다.

### Cluster Option ###
property no-quorum-policy="ignore" \
    stonith-enabled="false" \
    crmd-transition-delay="2s"

### Resource Defaults ###
rsc_defaults resource-stickiness="INFINITY" \
    migration-threshold="1"

### Primitive Configuration ###
primitive resource1 ocf:heartbeat:Dummy \
    op start interval="0s" timeout="300s" on-fail="restart" \
    op monitor interval="10s" timeout="60s" on-fail="restart" \
    op stop interval="0s" timeout="300s" on-fail="block"

primitive resource2 ocf:heartbeat:Dummy \
    op start interval="0s" timeout="300s" on-fail="restart" \
    op monitor interval="10s" timeout="60s" on-fail="restart" \
    op stop interval="0s" timeout="300s" on-fail="block"

primitive resource3 ocf:heartbeat:Dummy \
    op start interval="0s" timeout="300s" on-fail="restart" \
    op monitor interval="10s" timeout="60s" on-fail="restart" \
    op stop interval="0s" timeout="300s" on-fail="block"

### Resource Order ###
order rsc_order-1 0: resource1 resource2 resource3

2016.3.24 수정 : 이전 기사에서는 order에 "symmetrical = false"를 부여하고있었습니다 만,이 경우 Pacemaker-1.1 계에서는 다음 실험에서는 0과 INFINITY 동작의 차이가 없어졌다 (본 0 의 경우와 같은) 때문에 "symmetrical = false"를 삭제했습니다.

또한 Dummy 자원 (/usr/lib/ocf/resource.d/heartbeat/Dummy)가 시작 타이밍 (문맥)을 알기 쉽게하기 위해 start시 1 초 sleep하도록 개조하고 있습니다.

또한 order 제약 밖에 쓸 수 없기 때문에 pm01와 pm02를 동시에 시작하면 각 자원이 흩어지게 거동이 어려워집니다. 따라서 우선 pm01을 시작, 설정을 읽어 모든 자원이 pm01에서 시작하고 pm02를 시작합니다.

# crm_mon -rfA
～略～

Online: [ pm01 pm02 ]

Full list of resources:

resource1       (ocf::heartbeat:Dummy): Started pm01
resource2       (ocf::heartbeat:Dummy): Started pm01
resource3       (ocf::heartbeat:Dummy): Started pm01

Node Attributes:
* Node pm01:
    + pm02-eth1                         : up
* Node pm02:
    + pm01-eth1                         : up

Migration summary:
* Node pm01:
* Node pm02:

다음 명령을 실행하여 resource1 장애를 유발합니다.

# rm -f /var/run/resource-agents/Dummy-resource1.state

Pacemaker가 고장을 감지하고 F / O를 수행합니다.

# crm_mon -rfA
～略～

Online: [ pm01 pm02 ]

Full list of resources:

resource1       (ocf::heartbeat:Dummy): Started pm02 ★F/Oし、pm02で起動
resource2       (ocf::heartbeat:Dummy): Started pm01
resource3       (ocf::heartbeat:Dummy): Started pm01

Node Attributes:
* Node pm01:
    + pm02-eth1                         : up
* Node pm02:
    + pm01-eth1                         : up

Migration summary:
* Node pm01:
   resource1: migration-threshold=1 fail-count=1
* Node pm02:

Failed actions:
    resource1_monitor_10000 (node=pm01, call=52, rc=7, status=complete): not running

고장 (파일 삭제)를 발생시킨 시간 이후의 로그를 grep하여 두 노드에서 자원이 어떤 행동을했는지를 확인하자.
Pacemaker-1.0 계와 1.1 계에서 로그 형식이 다르기 때문에 다음 각각의 경우를 나타냅니다.

Pacemaker-1.0 계의 경우
○ pm01 로그

# egrep "lrmd:.*info: rsc:[A-Za-z0-9]+ (start|stop)" /var/log/ha-log
Jan  8 12:57:58 pm01 lrmd: [1518]: info: rsc:resource1 stop[53] (pid 4772)

○ PM02 のログ

# egrep "lrmd:.*info: rsc:[A-Za-z0-9]+ (start|stop)" /var/log/ha-log
Jan  8 12:57:58 pm02 lrmd: [1492]: info: rsc:resource1 start[21] (pid 7667)

Pacemaker-1.1 계의 경우
○ pm01 로그

# egrep "Operation .*_(start|stop)_" /var/log/ha-log
Mar 24 10:29:51 pm01 crmd[25011]:  notice: process_lrm_event: Operation resource1_stop_0: ok (node=pm01, call=21, rc=0, cib-update=72, confirmed=true)

○ PM02 のログ

# egrep "Operation .*_(start|stop)_" /var/log/ha-log
Mar 24 10:29:51 pm02 crmd[6357]:  notice: process_lrm_event: Operation resource1_start_0: ok (node=pm02, call=14, rc=0, cib-update=14, confirmed=true)

고장난 resource1가 pm01에서 정지 후 pm02에서 시작하고 F / O가 성공했음을 로그에서도 확인할 수있었습니다.

다음은 order 점수 값을 INFINITY로 변경하고 이전처럼 resource1 장애를 유발합니다.

order rsc_order-1 0: resource1 resource2 resource3

　　↓ 書き換え

order rsc_order-1 INFINITY: resource1 resource2 resource3

고장 후 crm_mon는 다음과 같이 될 것입니다.

# crm_mon -rfA
～略～

Online: [ pm01 pm02 ]

Full list of resources:

resource1       (ocf::heartbeat:Dummy): Started pm02 ★F/Oし、pm02で起動
resource2       (ocf::heartbeat:Dummy): Started pm01
resource3       (ocf::heartbeat:Dummy): Started pm01

Node Attributes:
* Node pm01:
    + pm02-eth1                         : up
* Node pm02:
    + pm01-eth1                         : up

Migration summary:
* Node pm01:
   resource1: migration-threshold=1 fail-count=1
* Node pm02:

Failed actions:
    resource1_monitor_10000 (node=pm01, call=60, rc=7, status=complete): not running

점수 값이 0 일 때처럼 pm02에서 resource1가 시작 (F / O)했습니다.
그러나 약간 거동이 조금 전과는 다른 것을 깨달았다 있을까요?
crm_mon을 잘 ~보고 있던 사람은 발견 할 수도 있지만, 실은 resource2,3도 resource1 고장에 끌려 다시 시작했습니다.

로그 (/ var / log / ha-log)에서 resource1 ~ 3의 거동을 확인하려고합니다.

Pacemaker-1.0 계의 경우
○ pm01 로그

# egrep "lrmd:.*info: rsc:[:A-Za-z0-9]+ (start|stop)" /var/log/ha-log
Jan  8 13:19:02 pm01 lrmd: [1518]: info: rsc:resource3 stop[61] (pid 5848) ★
Jan  8 13:19:02 pm01 lrmd: [1518]: info: rsc:resource2 stop[62] (pid 5849) ★
Jan  8 13:19:02 pm01 lrmd: [1518]: info: rsc:resource1 stop[63] (pid 5850)
Jan  8 13:19:04 pm01 lrmd: [1518]: info: rsc:resource2 start[64] (pid 5859) ★
Jan  8 13:19:05 pm01 lrmd: [1518]: info: rsc:resource3 start[66] (pid 5869) ★

○ PM02 のログ

# egrep "lrmd:.*info: rsc:[:A-Za-z0-9]+ (start|stop)" /var/log/ha-log
Jan  8 13:19:03 pm02 lrmd: [8126]: info: rsc:resource1 start[5] (pid 8154)

Pacemaker-1.1 계의 경우
○ pm01 로그

# egrep "Operation .*_(start|stop)_" /var/log/ha-log
Mar 24 10:33:11 pm01 crmd[25288]:  notice: process_lrm_event: Operation resource3_stop_0: ok ～略～ ★
Mar 24 10:33:13 pm01 crmd[25288]:  notice: process_lrm_event: Operation resource2_stop_0: ok ～略～ ★
Mar 24 10:33:15 pm01 crmd[25288]:  notice: process_lrm_event: Operation resource1_stop_0: ok ～略～
Mar 24 10:33:19 pm01 crmd[25288]:  notice: process_lrm_event: Operation resource2_start_0: ok ～略～ ★
Mar 24 10:33:21 pm01 crmd[25288]:  notice: process_lrm_event: Operation resource3_start_0: ok ～略～ ★

○ PM02 のログ

# egrep "Operation .*_(start|stop)_" /var/log/ha-log
Mar 24 10:33:15 pm02 crmd[6453]:  notice: process_lrm_event: Operation resource1_start_0: ok (node=pm02, call=14, rc=0, cib-update=11, confirmed=true)

★ 부분에서 이전과는 달리 resource2,3도 정지 → 시작을하고 있는지 알 수 있습니다.
각각 start 한 시간을 확인하면 resource1 → resource2 → resource3 순으로 시작한 것을 알 수 있습니다.

이것은 설정 한 order 제약이
" 절대 (= INFINITY) resource1 → resource2 → resource3의 순서로 시작 / 중지해야한다"
는 것이었다 때문에 고장에 의한 상태 변화에 따라 resource2 및 resource3를 중지 → 시작하는 거동이 때문입니다.

한편 점수 값이 0 인 경우의 order 제약
"가급적 (= 0) resource1 → resource2 → resource3의 순서로 시작 / 중지 '
라는 것이며, 고장으로 인한 상태 변화는 resource2 및 resource3에 영향을주지 않았습니다.

■ 실험 3 속성 값을 평가하는

location 제약에서 속성 값을 평가 해 봅니다.

CRM 설정은 하나의 Dummy 리소스를 location으로 배치 조건을 건 그냥 단순한 것을 사용합니다.

### Cluster Option ###
property no-quorum-policy="ignore" \
    stonith-enabled="false" \
    crmd-transition-delay="2s"

### Resource Defaults ###
rsc_defaults resource-stickiness="INFINITY" \
    migration-threshold="1"

### Primitive Configuration ###
primitive resource1 ocf:heartbeat:Dummy \
    op start interval="0s" timeout="300s" on-fail="restart" \
    op monitor interval="10s" timeout="60s" on-fail="restart" \
    op stop interval="0s" timeout="300s" on-fail="block"

### Resource Location ###
location rsc_location-1 resource1 \
    rule -INFINITY: not_defined my_attribute or my_attribute lt 100

이를 Pacemaker에 반영합니다.
하지만, 다음과 같이 resource1는 중지 된 상태가 될 것입니다 (★ 부분).

# crm_mon -rfA
～略～
Online: [ pm01 pm02 ]

Full list of resources:

resource1       (ocf::heartbeat:Dummy): Stopped ★resource1は停止したまま

Node Attributes:
* Node pm01:
    + pm02-eth1                         : up
    + pm02-eth2                         : up
* Node pm02:
    + pm01-eth1                         : up
    + pm01-eth2                         : up

Migration summary:
* Node pm01:
* Node pm02:

이것은 CRM 설정의 다음 부분에서 "my_attribute"라는 속성 값이 존재하지 않는 경우 또는 100 이하인 경우에는 시작할 수 없다고 제약하고 있기 때문입니다.

위치 rsc_location-1 리소스 1 \
    규칙 무한대 : not_defined my_attribute 또는 my_attribute LT (100)

resource1를 시작하려면 다음 crm_attribute 명령으로 속성 값을 수동으로 정의합니다.
두 노드에서 실행해도 괜찮습니다.
-N 옵션에서 속성 값을 생성하는 노드를 -n으로 속성 값 이름을 -v 값을 설정합니다.
-l은 reboot 또는 forever 중 하나에서, reboot는 그 속성 값이 Pacemaker 정지로 속성치가 삭제되는 것을 나타냅니다. forever은 Pacemaker 종료 된 후에도 속성 값을 담고 있습니다.

# crm_attribute -N pm01 -n my_attribute -v 100 -l reboot

속성 값이 설정되면 resource1가 시작합니다.

# crm_mon -rfA
～略～

Online: [ pm01 pm02 ]

Full list of resources:

resource1       (ocf::heartbeat:Dummy): Started pm01 ★resource1が起動

Node Attributes:
* Node pm01:
    + my_attribute                      : 100 ★属性値が100で設定された
    + pm02-eth1                         : up
    + pm02-eth2                         : up
* Node pm02:
    + pm01-eth1                         : up
    + pm01-eth2                         : up

Migration summary:
* Node pm01:
* Node pm02:

속성 값의 값을 10으로 변경하려고합니다.

# crm_attribute -N pm01 -n my_attribute -v 10 -l reboot

resource1가 중지 생각합니다.

# crm_mon -rfA
～略～
Online: [ pm01 pm02 ]

Full list of resources:

resource1       (ocf::heartbeat:Dummy): Stopped ★resource1が停止

Node Attributes:
* Node pm01:
    + my_attribute                      : 10 ★属性値が10に変更
    + pm02-eth1                         : up
    + pm02-eth2                         : up
* Node pm02:
    + pm01-eth1                         : up
    + pm01-eth2                         : up

Migration summary:
* Node pm01:
* Node pm02:

또한, 실제로 본 실험과 같이 속성 값을 수동으로 설정하거나 변경하는 경우는 거의없고, NW 감시 (ocf : pacemaker : pingd)과 디스크 모니터링 (ocf : pacemaker : diskd)가 내부적으로 사용 하고 있습니다.

■ おわりに

3 회에 걸친 "움직여 이해 Pacemaker - CRM 설정 편 ~」은 이번으로 끝입니다.

끝까지 읽어 주신 분은 예제 설정 파일 은 물론, 데모 환경의 CRM 설정 파일 도 읽을 수있게되어 있다고 생각합니다.

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Pacemaker OVerview

GrooveYOU 2016. 4. 18. 12:38

2016. 4. 18. 12:38

Pacemaker는 오픈 소스 소프트웨어 (OSS)로 개발되어, HA 클러스터 소프트웨어입니다. 이전에는 'Heartbeat'라는 이름으로 개발 된 소프트웨어의 후속입니다.

HA 클러스터는 여러 대의 컴퓨터를 연결 전체에서 하나의 컴퓨터처럼 대접하는 것으로, 시스템 전체의 가동률을 높이는 기술입니다.
HA는 "High Availability"(= 고 가용성)의 약자로 말 그대로 가용성 (*)가 높은 상태를 나타냅니다. * 가용성은 고장 등을 포함한 시스템이 어떻게 멈추지 않고 가동하고 있는지의 정도.

Pacemaker는 여러 대의 컴퓨터를 NW 등으로 연계하여 고장을 감지 한 후 다른 컴퓨터에 자동적으로 대납 (장애)시키는 등 '고 가용성'을 제공합니다.

Contents [ hide ]

Pacemaker의 기능과 대응 가능한 고장

Pacemaker는 크게 다음 다섯 가지 기능을 가지고 있습니다.
이렇게하면 서버에서 발생할 수있는 대부분의 고장에 있습니다.

응용 프로그램 모니터링 및 제어 기능
- Apache, nginx, Tomcat, JBoss, PostgreSQL, Oracle, MySQL, 파일 시스템 관리, 가상 IP 주소 제어 등 많은 리소스 에이전트 (RA)를 포함하고 있습니다. 또한 RA를 자작하면 어떤 응용 프로그램에서도 모니터링 할 수 있습니다.
네트워크 모니터링 및 제어 기능
- 정기적으로 지정된 대상에 ping을 전송하여 네트워크 연결 상태를 모니터링 할 수 있습니다.
노드 모니터링 기능
- 정기적으로 서로 하트 비트 통신 노드 모니터링을합니다. 또한 STONITH 기능은 통신 불가능한 상태가 된 노드의 전원을 강제로 중지하고 양계 상태 (split-brain)를 피할 수 있습니다.
자기 감시 기능
- Pacemaker 관련 프로세스를 종료 할 때 영향 정도에 따라 적절한 프로세스를 재시작하거나 장애를 실시합니다. 또한 watchdog 기능을 함께 사용하여 메인 프로세스 정지시 자동으로 OS 재시작 (및 장애)를 실행합니다.
디스크 모니터링 및 제어 기능
- 지정된 디스크 읽기를 정기적으로 실시하고 디스크 액세스 상태를 모니터링합니다.

다음 공유 디스크 구성 Pacemaker가 대응할 수있는 고장 부분의 이미지입니다. (×의 개소의 고장에 대응할 수 있습니다.)

fail_example

일반적인 클러스터 구성

Pacemaker는 다양한 구성의 HA 클러스터에 대응하고 있습니다.

대체적으로 "데이터의 인계 방법"및 "노드 대수」에 따라 클러스터 구성을 분류 할 수 있습니다.
다음에 Pacemaker가 대응 가능한 클러스터 구성을 보여줍니다.

데이터 인계 방법에 따른 분류

공유 구성
- 두 노드 모두에서 액세스 할 수있는 공유 디스크를 이용해 데이터를 통해 구성입니다. 옛부터 많은 시스템에서 사용되는 가장 일반적인 구성입니다.
비공유 구성 (PG-REX / DRBD 이용)
- 공유 디스크는 사용하지 않고 소프트웨어로 데이터 복제 기능을 사용하여 데이터를 통해 구성입니다.Pacemaker는 PostgreSQL의 스트리밍 복제 기능 에 의한 PG-REX 구성 , 그리고 DRBD 를 이용한 구성에 대응하고 있습니다. 비싼 공유 디스크가 필요하지 않기 때문에 저렴하게 시스템을 구축 할 수 있습니다.

노드 대수에 따른 분류

1 + 1 구성
- 2 대의 서버를 Active 서버와 Standby 서버로, Active 서버의 고장시 Standby 서버로 장애를 구성합니다.많은 시스템에서 사용되는 가장 일반적인 구성입니다.
N + 1 구성
- N 대 (2 대 이상) 서버를 Active 하나를 Standby로 각 Active 서버의 고장시에는 하나의 Standby 서버에 장애 구성입니다. Standby 서버를 통합함으로써 서버 활용도를 높이고 낭비를 최소화합니다. 여러 대의 고장시에는 하나의 Standby 여러 서비스를 실행하는 축퇴 운전입니다. (*)
N + M 구성
- N 대의 서버를 Active, M 대의 서버를 Standby로 구성되어 있습니다. Pacemaker-1.1 이후에 대응했습니다. 서버 가동률과 타락한시 성능 저하의 균형에 의해 임의의 대수로 구성 할 수 있습니다.

(*) Pacemaker-1.1 이후로는 두 번째 이후의 장애를 억제하는 설정도 가능합니다.

Pacemaker와 가동률

Pacemaker는 장애시 해당 자원의 중지, 시작을 실행합니다.
응용 프로그램에 따라 다르지만 대체로 수십 초에서 몇 분에 장애가 가능합니다.

따라서 Pacemaker는 대체로 ~ 99.999 %의 가동률 (* 1)를 실현 가능 (* 2)입니다.
99.9999 %는 고장 패턴에 따라 초과 할 수 있습니다.

* 1 일정 기간 동안 시스템이 실행되는 시간의 비율. 가용성의 지표가된다.
* 2 어디 까지나 년에 1 ~ 2 회 고장이 발생한다고 가정했을 경우의 기준입니다. 자원 구성, 애플리케이션, 고장 발생 빈도 등에 의해 실현 될 수없는 경우도 있습니다.

다음에 가동률과 구체적인 가동 시간 (연간) Pacemaker에서의 대응 여부를 정리해 보겠습니다.

가동률 [%]	허용되는 연간 정지 시간	실현 방법 이미지
99	약 3.6 일	이상이 있으면 메일이 발송되며 운영자가 달려 대응 정도로 OK
99.9	약 8.7 시간	운영자가 가까이 있으면 좋지만, 먼 곳이라 어려울지도. 수동도 좋지만, Pacemaker 가 갖고 싶어 나 할까.
99.99	약 52 분	상용 시스템은 대체로이 정도를 요구 되는가? Pacemaker 에 대응 가능.
99.999	약 5 분	이른바 파이브 나인. Pacemaker 에 대응 가능.
99.9999	31 초	자원 구성 고장 패턴에 따라 어떻게 든 Pacemaker에 대응할 수있는 ...? 하드웨어 및 가상 머신 레벨에서 FT (내결함성)도 원하는 곳.

Pacemaker 버전의 선택

Pacemaker는 크게 "리소스 제어 기능" 과 "클러스터 제어 기능" 의 2 개의 내부 구성 요소가 나누어 져있어 각각 선택 결합 할 수 있습니다.

각각 메이저 버전의 차이도 포함 해 다음 옵션이 있습니다.

리소스 제어 기능

Pacemaker 1.0 계
Pacemaker 1.1 계 (최신)

클러스터 제어 기능

Heartbeat 3 계
Corosync 1 계
Corosync 2 계 (최신)

한마디로 Pacemaker해도 위 2 × 3 = 6 개의 조합이 존재하는 것입니다.

구성 요소와 버전이 다르면 당연히 조작 방법이나 행동이 조금씩 달라집니다.
동안 안정된 동작을하지 or 원래 지원되지 않는 조합도 있습니다.

Linux-HA Japan 커뮤니티로는 다음 2 패턴의 조합을 권장하고 있습니다.

추천 조합 1 : OS, 미들 버전 모두 현재를 사용할 수있는 사람을위한
- 리소스 제어 기능 : Corosync 2 계
- 클러스터 제어 기능 : Pacemaker 1.1 계
  - 대응 OS : RHEL6.X 및 RHEL7.X (포함 RHEL 클론 OS)
  - 2014 년 12 월에이 조합의 저장소 패키지를 릴리스했습니다.
  - 주로 Corosync의 효율적인 노드 관리를 통해 2의 조합보다 동작이 빠르다 입니다.
  - 2 조합에서는 불가능한 구성, 동작이 새로운 기능 을 통해 가능합니다. (N + M 구성과 리소스 할당 전략 기능 등)
  - 다운로드 / 설치 방법은 여기

추천 조합 2 : 오래된 OS를 사용하거나 이미 Pacemaker (+ Heartbeat)를 사용하고 있으며, 노하우 등을 유용하고 사람을위한
- 리소스 제어 기능 : Pacemaker 1.0 계
- 클러스터 제어 기능 : Heartbeat 3 계
  - 대응 OS : RHEL5.X 및 RHEL6.X (포함 RHEL 클론 OS)
  - 2011 년 출시 이후 상용 시스템에 채용을 포함한 실적이 풍부합니다.
  - 노하우도 많이 축적되어 있습니다.
  - 현재 새로운 기능의 추가는 실시하지 않습니다.
  - 저장소 패키지의 최신은 2014 년 8 월 출시 Pacemaker 1.0.13-2.1 입니다. 다운로드는 여기

자원 및 자원 에이전트

Pacemaker는 다양한 응용 프로그램을 HA 클러스터링 할 수 있습니다.
Pacemaker는 제어 대상을 자원 이라고합니다.

각 자원의 시작 / 감시 / 정지 등의 제어는 자원 에이전트 (RA) 라는 각 리소스 전용 모듈을 통해 이루어집니다. 전용 모듈을 통한 것으로, 각각의 애플리케이션 제어 방법의 차이를 랩하고 Pacemaker에서 통일적으로 취급 할 수 있도록하고 있습니다.

Pacemaker에는 Apache, PostgreSQL, Oracle, MySQL, Tomcat 가상 IP 주소, 파일 시스템 등 여러 리소스 에이전트가 처음부터 포함 되어 있습니다.

또한 자원 에이전트는 많은 쉘 스크립트로 작성되어 있으며, Open Cluster Framework (OCF)라는 사양 에 따르면 자신의 물건을 만들어 사용할 수도 있습니다.
OCF는 정의 할 메소드 (start / monitor 등) 및 반환 할 결과 등의 규정이되어 있습니다. 방법과 결과 등의 규정을 따른다면 구현하는 프로그램 언어는 묻지 않습니다. 그러나 배포판에 의존하지 않는, 예를 들어 bash가 아닌 sh에서 설명하는 등의 배려가 필요합니다.

좌우 분열과 배타 제어

HA 클러스터에서 리소스를 클러스터에 하나만 유지하는 것이 매우 중요합니다.
예를 들어, 공유 디스크를 갖는 이른바 공유 구성에서 여러 서버에서 동시에 마운트 / 액세스 해 버리면 공유 디스크 파일 시스템은 파괴되고 데이터가 손실 될 수 있습니다. 또한 공유 아무것도 구성에서도 예를 들면 DBMS가 여러 서버에서 실행하면 동일한 세그먼트에 여러 DBMS가 존재하게되고, 클라이언트에서 데이터가 분산되어 버렸 데이터 불일치가 발생합니다.

클러스터를 구성하는 서버 간의 통신이 정상적인 경우는 서버끼리 연계 할 수 있기 때문에 자원을 하나만 유지하는 것은 쉽습니다. 그러나 서버 사이의 통신 경로가 끊겼거나 노드가 다운되는 등 서버가 통신 할 수없는 경우에 위와 같은 문제가 발생합니다. 이 상태를 좌우 분열 이라고합니다.

splitbrain
그림 : 배타 제어를하지 않는 경우의 문제 (split-brain)

Pacemaker는 좌우 분열을 방지하려면 다음 세 가지의 배타 제어기구를 가지고 있습니다.
이 중에서 가장 신뢰성이 높고, 일반적인 것은 STONITH 입니다.

표 : 배타 제어의 종류

배타 제어 이름 (읽기)	요약	중지 실패에 대한 대응
STONITH (스토니스)	네트워크를 통해 상대 노드의 전원을 강제로 떨어 뜨린다	OK
SFEX (공상 과학이 엑스)	공유 디스크에 잠금 정보를 기록	NG
VIPcheck (빗뿌 체크)	가상 IP 주소로 ping을 수행 상대 노드의 상태를 확인하는	NG

배타 제어기구 중 STONITH 자원 중지에 실패했다 경우에도 유효 합니다.
일반적으로 장애 발생시 등의 자원 정지는 자원 에이전트에 의해 이루어 지지만, 이것은 어떤 이유로 실패 해 버리는 경우가 있습니다. (ex 프로세스가 완전히 무 반응 등)
자원은 클러스터에 하나만 유지해야하므로 제대로 정지 한 것을 확인 할 수없는 장애를 계속할 수 없으며이 경우 장애는 실패 버립니다.
그러나이 경우에도 STONITH를 사용하는 경우, 정지 실패한 노드의 전원을 강제로 끌 수 있도록 장애를 계속 서비스를 유지할 수 있습니다.

배타 제어에 대한 더 자세한 내용은 OSC2015 Tokyo / Fall 강연 「시도 기억 Pacemaker 입문 배타 제어 기능편」을 참고해주십시오.

'IBM PowerLinux > PaceMaker - Cluster' 카테고리의 다른 글

colocation location order 의미 (0)	2017.02.10
pacemaker (0)	2016.04.16
페이스 메이커 overall (0)	2016.04.13
클러스터 참고자료 (0)	2016.04.13
Fencing (0)	2016.04.13

pacemaker

GrooveYOU 2016. 4. 16. 13:39

2016. 4. 16. 13:39

http://clusterlabs.org/doc/en-US/Pacemaker/1.1-pcs/html-single/Clusters_from_Scratch/index.html#_what_is_stonith

'IBM PowerLinux > PaceMaker - Cluster' 카테고리의 다른 글

colocation location order 의미 (0)	2017.02.10
Pacemaker OVerview (0)	2016.04.18
페이스 메이커 overall (0)	2016.04.13
클러스터 참고자료 (0)	2016.04.13
Fencing (0)	2016.04.13

페이스 메이커 overall

GrooveYOU 2016. 4. 13. 02:08

2016. 4. 13. 02:08

http://gihyo.jp/admin/serial/01/pacemaker/0001

소개

Pacemaker하면, 심장 박동기와 마라톤 페이스 메이커, 모 DJ 기기라는 느낌이 있을지도 모르지만, 그것만이 아닙니다!

이 연재에서는 오픈 소스로 만들어진 HA 클러스터 소프트웨어 "Pacemaker" 을 소개에서 구축, 유지 보수 및 운영에 이르기까지 Linux-HA Japan 프로젝트 멤버 소개합니다. HA 클러스터는 문턱이 높다고 생각하는 사람은 많을 것입니다 만, 이 연재로 친숙한 소프트웨어라고 생각 주시면 감사하겠습니다. 기념할만한 연재 제 1 회에서는 Pacemaker의 개요, 역사를 소개합니다.

HA 클러스터는?

먼저 클러스터가 무엇인지 알아 봅시다. 클러스터는 원래 과일과 꽃의 술이라는 의미에서 처럼 모아지는 것을 것을 말합니다.

여러 대의 컴퓨터를 연결해 전체에서 하나의 컴퓨터처럼 대접하는 기술로 크게 신뢰성 향상을 목적으로 한 「고 가용성 (High Availability) " 계산 속도 향상을 목적으로 한 "HPC (High Performance Computing) " 처리의 부하 분산을 목적으로 한 "로드 밸런싱 (Load Balancing) "의 3 종류가 있습니다 만, Pacemaker는 고 가용성 클러스터 (HA 클러스터) 소프트웨어입니다.

그 HA 클러스터 소프트웨어 인 Pacemaker는 고장을 감지하면 대기 시스템에 서비스를 인계 할 (장애) 에 의해 서비스의 다운 타임을 최소화 할 수 있습니다. 기본 구성은 운용 시스템과 대기 계로 구성 1 + 1 구성이지만 여러 대의 (N) 의 운용 계 노드에 대해 대기 계 노드 또는 다중 (M) 하는 N + M 구성을 구축 할 수 있습니다.

그림 1　1 + 1 구성 예

그림 2　2 + 1 구성 예

Pacemaker의 기본 기능은?

Pacemaker의 2 대 기본 기능을 소개합시다.

클러스터 제어 기능

"클러스터 상태를 전파 통신" "클러스터에 노드 참여 결정" "클러스터 노드 간의 정보 동기화" "일정 간격으로 상대 노드와 통신 생사 확인 ' 등을 실시하는 것이 클러스터 제어 기능입니다. 생사 확인 통신은 상호 통신 (하트 비트 통신) 라고하는데, 이것이 끊어 때 상대가 고장난 것으로 판단하고 장애 처리를 실시합니다.

말하자면 클러스터 제어 기능은 노드 간의 통신 · 관리 및 Pacemaker 전체 처리 관련 HA 클러스터 미만의 일을 할 수있는 토대 기능입니다.

그림 3　노드 감시 (클러스터 제어 기능)

리소스 제어 기능

일정한 간격으로 자원을 모니터링하고 정상적으로 작동하지 않는다고 판단하는 경우에 자원의 장애 처리를 실시하는 것이 리소스 제어 기능입니다.

전술 한 클러스터 제어 기능이라는 토대 위에서 리소스 제어 기능이 작동합니다.

그림 4　자원 모니터링 (리소스 모니터링 기능)

는, 「자원」은 뭐야? 의문으로 생각하는 사람이 있는지 생각하기 때문에 뒤늦게 간단하게 설명합시다. 여기서 자원은 Pacemaker가 제어 대상으로하는 응용 프로그램, 네트워크, 디스크 등을 나타냅니다.

예를 들어 PostgreSQL에 따르면 DB 서버의 HA 클러스터 시스템을 구축 할 경우에는 PostgreSQL은 '자원' 입니다. Pacemaker는 PostgreSQL 등의 자원을 자원 에이전트를 통해 시작 (start), 정지 (stop), 모니터 (monitor) 를 실행 리소스 제어합니다.

는, "자원 에이전트" 라는 또한 이해하기 어려운 말이 나오고 있었어요. 자원 에이전트는 자원과 Pacemaker를 중개하는 프로그램에서 주로 쉘 스크립트로 작성되어 있습니다.

PostgreSQL의 예에서 자원 에이전트 모니터링 (monitor) 의 개요를 설명하자. 자원 에이전트는 Pacemaker 본체에서 " monitor " 라는 명령을받습니다. 그 명령에서 PostgreSQL 본체에 대해 " select now () " SQL 문을 실행 성공 여부에 자원의 동작을 감시하고있는 것입니다.

자원 에이전트는 자작도 가능하지만, Web 계, DB 시스템, 네트워크 시스템,파일 시스템 계 등 다수의 자원 에이전트가 Pacemaker에는 표준으로 준비되어 다양한 관리 방법이 구현되어 있습니다. 자주 응용 프로그램 모니터링 스크립트를 고리 고리 자작했다는 얘기를 듣고 있지만 Pacemaker를 사용하면 그런 수고를 할 필요가 없습니다.

Pacemaker라고 어떻게 태어나요?

여기에서 Pacemaker의 역사를 소개합시다.

Pacemaker는 같은 오픈 소스 인 Heartbeat의 후계 소프트웨어입니다. 1999 년 최초의 Heartbeat가 출시 된 Heartbeat 버전 1. 0은 2003 년에 출시되었습니다. 이 시점에서는 상대 노드를 모니터링하는 등의 클러스터 제어 기능 밖에 없습니다 만, 리소스 제어 기능을 가진 Heartbeat 버전 2가 2005 년에 발표 된 것입니다.

이대로 버전 3이 개발되는 것으로 생각했는데, Heartbeat 리소스 제어 기능 (CRM : Cluster Resource Manager) 의 메인테이너 인 Andrew Beekhof (앤드류 비코후) 씨는 2007 년에 리소스 모니터링 기능을 "Pacemaker" 라는 새로운 제품으로 Heartbeat에서 독립시키는 것을 선언했습니다. 그리고 2008 년에 Pacemaker 버전 1. 0이 발표 된 것입니다.

이거 커뮤니티의 싸움 이별? 로 돌아서 생각해 버릴지도 모르지만, 그렇지는 않습니다. 구성 요소의 공통화하고, 이 자원 제어 기능을 다른 클러스터 제어 기능의 소프트웨어에서도 사용할 수 있도록 선택을 늘리려는 긍정적 인 생각입니다!

"Heartbeat"이 심장 · 고동을 의미하는 말에 대해 이 새로운 제품을 맥박 조정기의 뜻이다 "Pacemaker"로 명명 한 것은 센스로 통행 네요.

그 Pacemaker하지만 앞서 언급했듯이 리소스 제어 기능 만이므로, 혼자 HA 클러스터로 작동하지 않습니다. 다른 클러스터 제어 기능을 가진 소프트웨어와 결합해야하며, 현재는 선택 사항이 2 개 있습니다.

하나는 Heartbeat 버전 2에서 자원 제어 기능이 깎인 Heartbeat 버전 3 입니다. 재미있는 것은 버전 3과 번호는 올랐는데 단독 기능은 축소하고 말았지 만, 클러스터 제어 기능으로 앞으로도 유지되어갑니다.

또 하나는 OpenAIS 커뮤니티에서 개발 된 Corosync 입니다. Pacemaker이 'Heartbeat 버전 3」과 「Corosync " 클러스터 제어 기능이 선택 가능합니다.

Pacemaker는 이처럼 단독으로 동작시키는 것이 아니라 여러 구성 요소의 조합으로 제공되기 때문에 제품 이름은 "Pacemaker 플러스 ......" 라고 부르는? 라는 의문이 생길지도 모릅니다. 이 내용은 프로모션으로도 난테 부르게하거나 해당 고생했습니다.

고민에 고민 한 끝에 "Pacemaker + Heartbeat 버전 3" 도 "Pacemaker + Corosync" 도 Linux-HA Japan 프로젝트는 "Pacemaker" 라고 부르기로하고 있습니다. "Heartbeat" → "Heartbeat 버전 2" → "Pacemaker" 진화했다고 생각합니다.

그림 5　요소의 조합

Linux-HA Japan 프로젝트는?

제 1 회 연재 마지막으로 Linux-HA Japan 프로젝트를 소개합니다.

Linux-HA Japan 프로젝트는 Pacemaker의 전신 인 Heartbeat 일본의 한층 더 보급 전개를 목적으로 2007 년에 "Linux-HA (Heartbeat) 일본어 사이트" 의 설립에서 커뮤니티 활동이 창단되었습니다. Pacemaker 이행함에있어 프로젝트에서는 Pacemaker 정보 공개용으로 새로운 웹 사이트를 2010 년에 오픈하고 스터디 그룹, 이벤트 정보 등 수시로 사이트를 업데이트하고 있습니다.

Linux-HA Japan 프로젝트: URL : http : // linux-ha. sourceforge. jp /

메일 링리스트는 Pacemaker, Heartbeat 버전 3, Corosync, DRBD 등 HA 클러스터 관련 화제는 무엇이든 환영합니다. 광적인 클러스터 구성을 해 본 이야기 등 꼭 투고 해 주었으면하네요!

것으로, Pacemaker의 개요와 역사를 소개 했습니다만, 어땠습니까? 다음은실제로 Pacemaker의 설치와 몇 가지 설정을하고 그 과정을 설명하는 구축 기본 편을 소개하고자합니다.

칼럼 : Pacemaker 로고 이모저모 [그 1]

원래 본가 Pacemaker 사이트의 로고는 이것이었습니다.

그림 6　본가 Pacemaker 로고

그러나 이것으로는 그야말로 의료 기기이기 때문에 인상이 좋지 않아요. 따라서 Linux-HA Japan 프로젝트는 독자적으로 Pacemaker의 로고와 배너를 만들었습니다.

그림 7　Linux-HA Japan 오리지널 로고 배너

이건 무엇을 이미지하고 있는지 알 수 있습니까? 2011 년 간지이기도 한 토끼를 이미지하고있는 것입니다. 왜 토끼인가? 마라톤 페이스 메이커의 것을 래빗이라고도합니다. 이것을 역수로 취했습니다. 생동감 ·스피드 감 넘치는 토끼를 표현한 로고가 만들어지고 Linux-HA Japan 프로젝트의 얼굴이 된 것입니다.

그리고이 로고도 뜻밖의 이변이? 다음 연재 칼럼 "Pacemaker 로고 이모저모 [2] '에 계속 ...

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클러스터 참고자료

GrooveYOU 2016. 4. 13. 01:52

2016. 4. 13. 01:52

http://lustrekr.tistory.com/17

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Fencing

GrooveYOU 2016. 4. 13. 01:04

2016. 4. 13. 01:04

Fencing 이란,

공유 스토리지에서 부터 노드에 대한 연결을 끊는 것을 말한다. 연결을 끊는다는 건 I/O 를 단절 시킨다는 것이다. 그렇게 함으로써 데이터의 무결성을 보장한다.

Fence device 란,

공유 스토리지에서 노드를 단절시킬 수 있는 장치를 말한다.

노드를 공유 스토리지와 단절 시킬 수 있는 다양한 방법,

1. 원격 전원 스위치를 통해 노드 전원을 끄는 방법.
2. 스토리지 연결된 광케이블 스위치 포트를 비활성화 하는 방법.
3. 호스트의 SCSI 3 reservation 을 해지 하는 방법.

Fence agent 란,

Fence Device 와 접속하는 소프트웨어 프로그램으로써 노드의 공유 스토리지와의 연결을 단절 시키도록 Fence Device에게 요청하는 역할을 한다.
(위에서 말한 바와 같이 해당 노드의 전원을 끄거나, 다른 방법으로 공유 스토리지에 대한 접근을 제거하는 방법을 사용한다.)

다음은 RHEL 및 가상화 제품에서 사용할 수 있거나 사용 할 수 없는 Fence Agent 에 대한 Matirx 정보 입니다.

알아보기 쉽도록 색깔을 넣어 보았습니다. 주로 사용하는 Agent 는 IPMIlan 가 아닐까 합니다. 정말 많은 Agent가 있네요.

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[Linux] Pace Maker with Redhat7 구성

GrooveYOU 2016. 4. 6. 10:35

2016. 4. 6. 10:35

출처

http://clusterlabs.org/doc/en-US/Pacemaker/1.1-pcs/html-single/Clusters_from_Scratch/index.html

Pacemaker 1.1

Clusters from Scratch

Step-by-Step Instructions for Building Your First High-Availability Cluster

Edition 9

Andrew Beekhof

Primary author

Red Hat

andrew@beekhof.net

Raoul Scarazzini

Italian translation rasca@miamammausalinux.org

Dan Frîncu

Romanian translation df.cluster@gmail.com

Legal Notice

The text of and illustrations in this document are licensed under a Creative Commons Attribution–Share Alike 3.0 Unported license ("CC-BY-SA")^[1].

In accordance with CC-BY-SA, if you distribute this document or an adaptation of it, you must provide the URL for the original version.

In addition to the requirements of this license, the following activities are looked upon favorably:

If you are distributing Open Publication works on hardcopy or CD-ROM, you provide email notification to the authors of your intent to redistribute at least thirty days before your manuscript or media freeze, to give the authors time to provide updated documents. This notification should describe modifications, if any, made to the document.
All substantive modifications (including deletions) be either clearly marked up in the document or else described in an attachment to the document.
Finally, while it is not mandatory under this license, it is considered good form to offer a free copy of any hardcopy or CD-ROM expression of the author(s) work.

Abstract

The purpose of this document is to provide a start-to-finish guide to building an example active/passive cluster with Pacemaker and show how it can be converted to an active/active one.

The example cluster will use:

CentOS 7.1 as the host operating system
Corosync to provide messaging and membership services,
Pacemaker to perform resource management,
DRBD as a cost-effective alternative to shared storage,
GFS2 as the cluster filesystem (in active/active mode)

Given the graphical nature of the install process, a number of screenshots are included. However the guide is primarily composed of commands, the reasons for executing them and their expected outputs.

Table of Contents

Preface

1. Document Conventions

1.1. Typographic Conventions
1.2. Pull-quote Conventions
1.3. Notes and Warnings

2. We Need Feedback!

1. Read-Me-First

1.1. The Scope of this Document

1.2. What Is Pacemaker?

1.3. Pacemaker Architecture

1.3.1. Internal Components

1.4. Types of Pacemaker Clusters

2. Installation

2.1. Install CentOS 7.1

2.1.1. Boot the Install Image
2.1.2. Installation Options
2.1.3. Configure Network
2.1.4. Configure Disk
2.1.5. Configure Time Synchronization
2.1.6. Finish Install

2.2. Configure the OS

2.2.1. Verify Networking
2.2.2. Login Remotely
2.2.3. Apply Updates
2.2.4. Use Short Node Names

2.3. Repeat for Second Node

2.4. Configure Communication Between Nodes

2.4.1. Configure Host Name Resolution
2.4.2. Configure SSH

2.5. Install the Cluster Software

2.6. Configure the Cluster Software

2.6.1. Allow cluster services through firewall
2.6.2. Enable pcs Daemon
2.6.3. Configure Corosync

3. Pacemaker Tools

3.1. Simplify administration using a cluster shell
3.2. Explore pcs

4. Start and Verify Cluster

4.1. Start the Cluster
4.2. Verify Corosync Installation
4.3. Verify Pacemaker Installation

5. Create an Active/Passive Cluster

5.1. Explore the Existing Configuration
5.2. Add a Resource
5.3. Perform a Failover
5.4. Prevent Resources from Moving after Recovery

6. Add Apache as a Cluster Service

6.1. Install Apache
6.2. Create Website Documents
6.3. Enable the Apache status URL
6.4. Configure the Cluster
6.5. Ensure Resources Run on the Same Host
6.6. Ensure Resources Start and Stop in Order
6.7. Prefer One Node Over Another
6.8. Move Resources Manually

7. Replicate Storage Using DRBD

7.1. Install the DRBD Packages
7.2. Allocate a Disk Volume for DRBD
7.3. Configure DRBD
7.4. Initialize DRBD
7.5. Populate the DRBD Disk
7.6. Configure the Cluster for the DRBD device
7.7. Configure the Cluster for the Filesystem
7.8. Test Cluster Failover

8. Configure STONITH

8.1. What is STONITH?
8.2. Choose a STONITH Device
8.3. Configure the Cluster for STONITH
8.4. Example

9. Convert Cluster to Active/Active

9.1. Install Cluster Filesystem Software
9.2. Configure the Cluster for the DLM
9.3. Create and Populate GFS2 Filesystem
9.4. Reconfigure the Cluster for GFS2
9.5. Clone the IP address
9.6. Clone the Filesystem and Apache Resources
9.7. Test Failover

A. Configuration Recap

A.1. Final Cluster Configuration

A.2. Node List

A.3. Cluster Options

A.4. Resources

A.4.1. Default Options
A.4.2. Fencing
A.4.3. Service Address
A.4.4. DRBD - Shared Storage
A.4.5. Cluster Filesystem
A.4.6. Apache

B. Sample Corosync Configuration

C. Further Reading

D. Revision History

Index

List of Figures

1.1. The Pacemaker Stack
1.2. Internal Components
1.3. Active/Passive Redundancy
1.4. Shared Failover
1.5. N to N Redundancy
2.1. CentOS 7.1 Installation Welcome Screen
2.2. CentOS 7.1 Installation Summary Screen
2.3. CentOS 7.1 Console Prompt

List of Examples

5.1. The last XML you’ll see in this document

Preface

Table of Contents

1. Document Conventions

1.1. Typographic Conventions
1.2. Pull-quote Conventions
1.3. Notes and Warnings

2. We Need Feedback!

1. Document Conventions

This manual uses several conventions to highlight certain words and phrases and draw attention to specific pieces of information.

In PDF and paper editions, this manual uses typefaces drawn from the Liberation Fonts set. The Liberation Fonts set is also used in HTML editions if the set is installed on your system. If not, alternative but equivalent typefaces are displayed. Note: Red Hat Enterprise Linux 5 and later include the Liberation Fonts set by default.

1.1. Typographic Conventions

Four typographic conventions are used to call attention to specific words and phrases. These conventions, and the circumstances they apply to, are as follows.

Mono-spaced Bold

Used to highlight system input, including shell commands, file names and paths. Also used to highlight keys and key combinations. For example:

To see the contents of the file my_next_bestselling_novel in your current working directory, enter the cat my_next_bestselling_novel command at the shell prompt and press Enter to execute the command.

The above includes a file name, a shell command and a key, all presented in mono-spaced bold and all distinguishable thanks to context.

Key combinations can be distinguished from an individual key by the plus sign that connects each part of a key combination. For example:

Press Enter to execute the command.

Press Ctrl+Alt+F2 to switch to a virtual terminal.

The first example highlights a particular key to press. The second example highlights a key combination: a set of three keys pressed simultaneously.

If source code is discussed, class names, methods, functions, variable names and returned values mentioned within a paragraph will be presented as above, in mono-spaced bold. For example:

File-related classes include filesystem for file systems, file for files, and dir for directories. Each class has its own associated set of permissions.

Proportional Bold

This denotes words or phrases encountered on a system, including application names; dialog box text; labeled buttons; check-box and radio button labels; menu titles and sub-menu titles. For example:

Choose System → Preferences → Mouse from the main menu bar to launch Mouse Preferences. In the Buttons tab, select the Left-handed mouse check box and click Close to switch the primary mouse button from the left to the right (making the mouse suitable for use in the left hand).

To insert a special character into a gedit file, choose Applications → Accessories → Character Map from the main menu bar. Next, choose Search → Find… from the Character Map menu bar, type the name of the character in the Search field and click Next. The character you sought will be highlighted in the Character Table. Double-click this highlighted character to place it in the Text to copy field and then click the Copy button. Now switch back to your document and choose Edit → Paste from the gedit menu bar.

The above text includes application names; system-wide menu names and items; application-specific menu names; and buttons and text found within a GUI interface, all presented in proportional bold and all distinguishable by context.

Mono-spaced Bold Italic or Proportional Bold Italic

Whether mono-spaced bold or proportional bold, the addition of italics indicates replaceable or variable text. Italics denotes text you do not input literally or displayed text that changes depending on circumstance. For example:

To connect to a remote machine using ssh, type ssh username@domain.name at a shell prompt. If the remote machine is example.com and your username on that machine is john, type ssh john@example.com.

The mount -o remount file-system command remounts the named file system. For example, to remount the /home file system, the command is mount -o remount /home.

To see the version of a currently installed package, use the rpm -q package command. It will return a result as follows: package-version-release.

Note the words in bold italics above — username, domain.name, file-system, package, version and release. Each word is a placeholder, either for text you enter when issuing a command or for text displayed by the system.

Aside from standard usage for presenting the title of a work, italics denotes the first use of a new and important term. For example:

Publican is a DocBook publishing system.

1.2. Pull-quote Conventions

Terminal output and source code listings are set off visually from the surrounding text.

Output sent to a terminal is set in mono-spaced roman and presented thus:

books        Desktop   documentation  drafts  mss    photos   stuff  svn
books_tests  Desktop1  downloads      images  notes  scripts  svgs

Source-code listings are also set in mono-spaced roman but add syntax highlighting as follows:

package org.jboss.book.jca.ex1;

import javax.naming.InitialContext;

public class ExClient
{
   public static void main(String args[]) 
       throws Exception
   {
      InitialContext iniCtx = new InitialContext();
      Object         ref    = iniCtx.lookup("EchoBean");
      EchoHome       home   = (EchoHome) ref;
      Echo           echo   = home.create();

      System.out.println("Created Echo");

      System.out.println("Echo.echo('Hello') = " + echo.echo("Hello"));
   }
}

1.3. Notes and Warnings

Finally, we use three visual styles to draw attention to information that might otherwise be overlooked.

Note

Notes are tips, shortcuts or alternative approaches to the task at hand. Ignoring a note should have no negative consequences, but you might miss out on a trick that makes your life easier.

Important

Important boxes detail things that are easily missed: configuration changes that only apply to the current session, or services that need restarting before an update will apply. Ignoring a box labeled 'Important' will not cause data loss but may cause irritation and frustration.

Warning

Warnings should not be ignored. Ignoring warnings will most likely cause data loss.

2. We Need Feedback!

If you find a typographical error in this manual, or if you have thought of a way to make this manual better, we would love to hear from you! Please submit a report in Bugzilla ^[2] against the product Pacemaker.

When submitting a bug report, be sure to mention the manual's identifier: Clusters_from_Scratch

If you have a suggestion for improving the documentation, try to be as specific as possible when describing it. If you have found an error, please include the section number and some of the surrounding text so we can find it easily.

^[2]http://bugs.clusterlabs.org

Chapter 1. Read-Me-First

Table of Contents

1.1. The Scope of this Document

1.2. What Is Pacemaker?

1.3. Pacemaker Architecture

1.3.1. Internal Components

1.4. Types of Pacemaker Clusters

1.1. The Scope of this Document

Computer clusters can be used to provide highly available services or resources. The redundancy of multiple machines is used to guard against failures of many types.

This document will walk through the installation and setup of simple clusters using the CentOS distribution, version 7.1.

The clusters described here will use Pacemaker and Corosync to provide resource management and messaging. Required packages and modifications to their configuration files are described along with the use of the Pacemaker command line tool for generating the XML used for cluster control.

Pacemaker is a central component and provides the resource management required in these systems. This management includes detecting and recovering from the failure of various nodes, resources and services under its control.

When more in depth information is required and for real world usage, please refer to the Pacemaker Explained manual.

1.2. What Is Pacemaker?

Pacemaker is a cluster resource manager, that is, a logic responsible for a life-cycle of deployed software — indirectly perhaps even whole systems or their interconnections — under its control within a set of computers (a.k.a. nodes) and driven by prescribed rules.

It achieves maximum availability for your cluster services (a.k.a. resources) by detecting and recovering from node- and resource-level failures by making use of the messaging and membership capabilities provided by your preferred cluster infrastructure (either Corosync or Heartbeat), and possibly by utilizing other parts of the overall cluster stack.

Note

For the goal of minimal downtime a term high availability was coined and together with its acronym, HA, is well-established in the sector. To differentiate this sort of clusters from high performance computing (HPC) ones, should a context require it (apparently, not the case in this document), using HA cluster is an option.

Pacemaker’s key features include:

Detection and recovery of node and service-level failures
Storage agnostic, no requirement for shared storage
Resource agnostic, anything that can be scripted can be clustered
Supports fencing (also referred to as the STONITH acronym, deciphered later on) for ensuring data integrity
Supports large and small clusters
Supports both quorate and resource-driven clusters
Supports practically any redundancy configuration
Automatically replicated configuration that can be updated from any node
Ability to specify cluster-wide service ordering, colocation and anti-colocation
Support for advanced service types
- Clones: for services which need to be active on multiple nodes
- Multi-state: for services with multiple modes (e.g. master/slave, primary/secondary)
Unified, scriptable cluster management tools

1.3. Pacemaker Architecture

At the highest level, the cluster is made up of three pieces:

Non-cluster-aware components. These pieces include the resources themselves; scripts that start, stop and monitor them; and a local daemon that masks the differences between the different standards these scripts implement. Even though interactions of these resources when run as multiple instances can resemble a distributed system, they still lack the proper HA mechanisms and/or autonomous cluster-wide governance as subsumed in the following item.
Resource management. Pacemaker provides the brain that processes and reacts to events regarding the cluster. These events include nodes joining or leaving the cluster; resource events caused by failures, maintenance and scheduled activities; and other administrative actions. Pacemaker will compute the ideal state of the cluster and plot a path to achieve it after any of these events. This may include moving resources, stopping nodes and even forcing them offline with remote power switches.
Low-level infrastructure. Projects like Corosync, CMAN and Heartbeat provide reliable messaging, membership and quorum information about the cluster.

When combined with Corosync, Pacemaker also supports popular open source cluster filesystems.^[3]

Due to past standardization within the cluster filesystem community, cluster filesystems make use of a common distributed lock manager, which makes use of Corosync for its messaging and membership capabilities (which nodes are up/down) and Pacemaker for fencing services.

Figure 1.1. The Pacemaker Stack

1.3.1. Internal Components

Pacemaker itself is composed of five key components:

Cluster Information Base (CIB)
Cluster Resource Management daemon (CRMd)
Local Resource Management daemon (LRMd)
Policy Engine (PEngine or PE)
Fencing daemon (STONITHd)

Figure 1.2. Internal Components

The CIB uses XML to represent both the cluster’s configuration and current state of all resources in the cluster. The contents of the CIB are automatically kept in sync across the entire cluster and are used by the PEngine to compute the ideal state of the cluster and how it should be achieved.

This list of instructions is then fed to the Designated Controller (DC). Pacemaker centralizes all cluster decision making by electing one of the CRMd instances to act as a master. Should the elected CRMd process (or the node it is on) fail, a new one is quickly established.

The DC carries out the PEngine’s instructions in the required order by passing them to either the Local Resource Management daemon (LRMd) or CRMd peers on other nodes via the cluster messaging infrastructure (which in turn passes them on to their LRMd process).

The peer nodes all report the results of their operations back to the DC and, based on the expected and actual results, will either execute any actions that needed to wait for the previous one to complete, or abort processing and ask the PEngine to recalculate the ideal cluster state based on the unexpected results.

In some cases, it may be necessary to power off nodes in order to protect shared data or complete resource recovery. For this, Pacemaker comes with STONITHd.

Note

STONITH is an acronym for Shoot-The-Other-Node-In-The-Head, a recommended practice that misbehaving node is best to be promptly fenced (shut off, cut from shared resources or otherwise immobilized), and is usually implemented with a remote power switch.

In Pacemaker, STONITH devices are modeled as resources (and configured in the CIB) to enable them to be easily monitored for failure, however STONITHd takes care of understanding the STONITH topology such that its clients simply request a node be fenced, and it does the rest.

1.4. Types of Pacemaker Clusters

Pacemaker makes no assumptions about your environment. This allows it to support practically any redundancy configuration including Active/Active, Active/Passive, N+1, N+M, N-to-1 and N-to-N.

Figure 1.3. Active/Passive Redundancy

Two-node Active/Passive clusters using Pacemaker and DRBD are a cost-effective solution for many High Availability situations.

Figure 1.4. Shared Failover

By supporting many nodes, Pacemaker can dramatically reduce hardware costs by allowing several active/passive clusters to be combined and share a common backup node.

Figure 1.5. N to N Redundancy

When shared storage is available, every node can potentially be used for failover. Pacemaker can even run multiple copies of services to spread out the workload.

^[3]Even though Pacemaker also supports Heartbeat, the filesystems need to use the stack for messaging and membership, and Corosync seems to be what they’re standardizing on. Technically, it would be possible for them to support Heartbeat as well, but there seems little interest in this.

Chapter 2. Installation

2.1. Install CentOS 7.1

2.1.1. Boot the Install Image

Download the 4GB CentOS 7.1 DVD ISO. Use the image to boot a virtual machine, or burn it to a DVD or USB drive and boot a physical server from that.

After starting the installation, select your language and keyboard layout at the welcome screen.

Figure 2.1. CentOS 7.1 Installation Welcome Screen

2.1.2. Installation Options

At this point, you get a chance to tweak the default installation options.

Figure 2.2. CentOS 7.1 Installation Summary Screen

Ignore the SOFTWARE SELECTION section (try saying that 10 times quickly). The Infrastructure Server environment does have add-ons with much of the software we need, but we will leave it as a Minimal Install here, so that we can see exactly what software is required later.

2.1.3. Configure Network

In the NETWORK & HOSTNAME section:

Edit Host Name: as desired. For this example, we will use pcmk-1.localdomain.
Select your network device, press Configure…, and manually assign a fixed IP address. For this example, we’ll use 192.168.122.101 under IPv4 Settings (with an appropriate netmask, gateway and DNS server).
Flip the switch to turn your network device on.

Important

Do not accept the default network settings. Cluster machines should never obtain an IP address via DHCP, because DHCP’s periodic address renewal will interfere with corosync.

2.1.4. Configure Disk

By default, the installer’s automatic partitioning will use LVM (which allows us to dynamically change the amount of space allocated to a given partition). However, it allocates all free space to the / (aka. root) partition, which cannot be reduced in size later (dynamic increases are fine).

In order to follow the DRBD and GFS2 portions of this guide, we need to reserve space on each machine for a replicated volume.

Enter the INSTALLATION DESTINATION section, ensure the hard drive you want to install to is selected, select I will configure partitioning, and press Done.

In the MANUAL PARTITIONING screen that comes next, click the option to create mountpoints automatically. Select the / mountpoint, and reduce the desired capacity by 1GiB or so. Select Modify… by the volume group name, and change the Size policy: to As large as possible, to make the reclaimed space available inside the LVM volume group. We’ll add the additional volume later.

2.1.5. Configure Time Synchronization

It is highly recommended to enable NTP on your cluster nodes. Doing so ensures all nodes agree on the current time and makes reading log files significantly easier.

CentOS will enable NTP automatically. If you want to change any time-related settings (such as time zone or NTP server), you can do this in the TIME & DATE section.

2.1.6. Finish Install

Select Begin Installation. Once it completes, set a root password, and reboot as instructed. For the purposes of this document, it is not necessary to create any additional users. After the node reboots, you’ll see a login prompt on the console. Login using root and the password you created earlier.

Figure 2.3. CentOS 7.1 Console Prompt

Note

From here on, we’re going to be working exclusively from the terminal.

2.2. Configure the OS

2.2.1. Verify Networking

Ensure that the machine has the static IP address you configured earlier.

[root@pcmk-1 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 52:54:00:d7:d6:08 brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.101/24 brd 192.168.122.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::5054:ff:fed7:d608/64 scope link
       valid_lft forever preferred_lft forever

Note

If you ever need to change the node’s IP address from the command line, follow

[root@pcmk-1 ~]# vi /etc/sysconfig/network-scripts/ifcfg-${device} # manually edit as desired
[root@pcmk-1 ~]# nmcli dev disconnect ${device}
[root@pcmk-1 ~]# nmcli con reload ${device}
[root@pcmk-1 ~]# nmcli con up ${device}

This makes NetworkManager aware that a change was made on the config file.

Next, ensure that the routes are as expected:

[root@pcmk-1 ~]# ip route
default via 192.168.122.1 dev eth0  proto static  metric 100
192.168.122.0/24 dev eth0  proto kernel  scope link  src 192.168.122.101  metric 100

If there is no line beginning with default via, then you may need to add a line such as

GATEWAY="192.168.122.1"

to the device configuration using the same process as described above for changing the IP address.

Now, check for connectivity to the outside world. Start small by testing whether we can reach the gateway we configured.

[root@pcmk-1 ~]# ping -c 1 192.168.122.1
PING 192.168.122.1 (192.168.122.1) 56(84) bytes of data.
64 bytes from 192.168.122.1: icmp_req=1 ttl=64 time=0.249 ms

 --- 192.168.122.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.249/0.249/0.249/0.000 ms

Now try something external; choose a location you know should be available.

[root@pcmk-1 ~]# ping -c 1 www.google.com
PING www.l.google.com (173.194.72.106) 56(84) bytes of data.
64 bytes from tf-in-f106.1e100.net (173.194.72.106): icmp_req=1 ttl=41 time=167 ms

 --- www.l.google.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 167.618/167.618/167.618/0.000 ms

2.2.2. Login Remotely

The console isn’t a very friendly place to work from, so we will now switch to accessing the machine remotely via SSH where we can use copy and paste, etc.

From another host, check whether we can see the new host at all:

beekhof@f16 ~ # ping -c 1 192.168.122.101
PING 192.168.122.101 (192.168.122.101) 56(84) bytes of data.
64 bytes from 192.168.122.101: icmp_req=1 ttl=64 time=1.01 ms

--- 192.168.122.101 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.012/1.012/1.012/0.000 ms

Next, login as root via SSH.

beekhof@f16 ~ # ssh -l root 192.168.122.101
The authenticity of host '192.168.122.101 (192.168.122.101)' can't be established.
ECDSA key fingerprint is 6e:b7:8f:e2:4c:94:43:54:a8:53:cc:20:0f:29:a4:e0.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.122.101' (ECDSA) to the list of known hosts.
root@192.168.122.101's password:
Last login: Tue Aug 11 13:14:39 2015
[root@pcmk-1 ~]#

2.2.3. Apply Updates

Apply any package updates released since your installation image was created:

[root@pcmk-1 ~]# yum update

2.2.4. Use Short Node Names

During installation, we filled in the machine’s fully qualified domain name (FQDN), which can be rather long when it appears in cluster logs and status output. See for yourself how the machine identifies itself:

[root@pcmk-1 ~]# uname -n
pcmk-1.localdomain

We can use the hostnamectl tool to strip off the domain name:

[root@pcmk-1 ~]# hostnamectl set-hostname $(uname -n | sed s/\\..*//)

Now, check that the machine is using the correct name:

[root@pcmk-1 ~]# uname -n
pcmk-1

2.3. Repeat for Second Node

Repeat the Installation steps so far, so that you have two nodes ready to have the cluster software installed.

For the purposes of this document, the additional node is called pcmk-2 with address 192.168.122.102.

2.4. Configure Communication Between Nodes

2.4.1. Configure Host Name Resolution

Confirm that you can communicate between the two new nodes:

[root@pcmk-1 ~]# ping -c 3 192.168.122.102
PING 192.168.122.102 (192.168.122.102) 56(84) bytes of data.
64 bytes from 192.168.122.102: icmp_seq=1 ttl=64 time=0.343 ms
64 bytes from 192.168.122.102: icmp_seq=2 ttl=64 time=0.402 ms
64 bytes from 192.168.122.102: icmp_seq=3 ttl=64 time=0.558 ms

--- 192.168.122.102 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2000ms
rtt min/avg/max/mdev = 0.343/0.434/0.558/0.092 ms

Now we need to make sure we can communicate with the machines by their name. If you have a DNS server, add additional entries for the two machines. Otherwise, you’ll need to add the machines to /etc/hosts on both nodes. Below are the entries for my cluster nodes:

[root@pcmk-1 ~]# grep pcmk /etc/hosts
192.168.122.101 pcmk-1.clusterlabs.org pcmk-1
192.168.122.102 pcmk-2.clusterlabs.org pcmk-2

We can now verify the setup by again using ping:

[root@pcmk-1 ~]# ping -c 3 pcmk-2
PING pcmk-2.clusterlabs.org (192.168.122.101) 56(84) bytes of data.
64 bytes from pcmk-1.clusterlabs.org (192.168.122.101): icmp_seq=1 ttl=64 time=0.164 ms
64 bytes from pcmk-1.clusterlabs.org (192.168.122.101): icmp_seq=2 ttl=64 time=0.475 ms
64 bytes from pcmk-1.clusterlabs.org (192.168.122.101): icmp_seq=3 ttl=64 time=0.186 ms

--- pcmk-2.clusterlabs.org ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2001ms
rtt min/avg/max/mdev = 0.164/0.275/0.475/0.141 ms

2.4.2. Configure SSH

SSH is a convenient and secure way to copy files and perform commands remotely. For the purposes of this guide, we will create a key without a password (using the -N option) so that we can perform remote actions without being prompted.

Warning

Unprotected SSH keys (those without a password) are not recommended for servers exposed to the outside world. We use them here only to simplify the demo.

Create a new key and allow anyone with that key to log in:

Creating and Activating a new SSH Key

[root@pcmk-1 ~]# ssh-keygen -t dsa -f ~/.ssh/id_dsa -N ""
Generating public/private dsa key pair.
Your identification has been saved in /root/.ssh/id_dsa.
Your public key has been saved in /root/.ssh/id_dsa.pub.
The key fingerprint is:
91:09:5c:82:5a:6a:50:08:4e:b2:0c:62:de:cc:74:44 root@pcmk-1.clusterlabs.org
The key's randomart image is:
+--[ DSA 1024]----+
|==.ooEo..        |
|X O + .o o       |
| * A    +        |
|  +      .       |
| .      S        |
|                 |
|                 |
|                 |
|                 |
+-----------------+
[root@pcmk-1 ~]# cp ~/.ssh/id_dsa.pub ~/.ssh/authorized_keys

Install the key on the other node:

[root@pcmk-1 ~]# scp -r ~/.ssh pcmk-2:
The authenticity of host 'pcmk-2 (192.168.122.102)' can't be established.
ECDSA key fingerprint is a4:f5:b2:34:9d:86:2b:34:a2:87:37:b9:ca:68:52:ec.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'pcmk-2,192.168.122.102' (ECDSA) to the list of known hosts.
root@pcmk-2's password:
id_dsa.pub                           100%  616     0.6KB/s   00:00
id_dsa                               100%  672     0.7KB/s   00:00
known_hosts                          100%  400     0.4KB/s   00:00
authorized_keys                      100%  616     0.6KB/s   00:00

Test that you can now run commands remotely, without being prompted:

[root@pcmk-1 ~]# ssh pcmk-2 -- uname -n
pcmk-2

2.5. Install the Cluster Software

Fire up a shell on both nodes and run the following to install pacemaker, and while we’re at it, some command-line tools to make our lives easier:

# yum install -y pacemaker pcs psmisc policycoreutils-python

Important

This document will show commands that need to be executed on both nodes with a simple # prompt. Be sure to run them on each node individually.

Note

This document uses pcs for cluster management. Other alternatives, such as crmsh, are available, but their syntax will differ from the examples used here.

2.6. Configure the Cluster Software

2.6.1. Allow cluster services through firewall

On each node, allow cluster-related services through the local firewall:

# firewall-cmd --permanent --add-service=high-availability
success
# firewall-cmd --reload
success

Note

If you are using iptables directly, or some other firewall solution besides firewalld, simply open the following ports, which can be used by various clustering components: TCP ports 2224, 3121, and 21064, and UDP port 5405.

If you run into any problems during testing, you might want to disable the firewall and SELinux entirely until you have everything working. This may create significant security issues and should not be performed on machines that will be exposed to the outside world, but may be appropriate during development and testing on a protected host.

To disable security measures:

[root@pcmk-1 ~]# setenforce 0
[root@pcmk-1 ~]# sed -i.bak "s/SELINUX=enforcing/SELINUX=permissive/g" /etc/selinux/config
[root@pcmk-1 ~]# systemctl disable firewalld.service
[root@pcmk-1 ~]# systemctl stop firewalld.service
[root@pcmk-1 ~]# iptables --flush

2.6.2. Enable pcs Daemon

Before the cluster can be configured, the pcs daemon must be started and enabled to start at boot time on each node. This daemon works with the pcs command-line interface to manage synchronizing the corosync configuration across all nodes in the cluster.

Start and enable the daemon by issuing the following commands on each node:

# systemctl start pcsd.service
# systemctl enable pcsd.service
ln -s '/usr/lib/systemd/system/pcsd.service' '/etc/systemd/system/multi-user.target.wants/pcsd.service'

The installed packages will create a hacluster user with a disabled password. While this is fine for running pcs commands locally, the account needs a login password in order to perform such tasks as syncing the corosync configuration, or starting and stopping the cluster on other nodes.

This tutorial will make use of such commands, so now we will set a password for the hacluster user, using the same password on both nodes:

# passwd hacluster
Changing password for user hacluster.
New password:
Retype new password:
passwd: all authentication tokens updated successfully.

Note

Alternatively, to script this process or set the password on a different machine from the one you’re logged into, you can use the --stdin option for passwd:

[root@pcmk-1 ~]# ssh pcmk-2 -- 'echo redhat1 | passwd --stdin hacluster'

2.6.3. Configure Corosync

On either node, use pcs cluster auth to authenticate as the hacluster user:

[root@pcmk-1 ~]# pcs cluster auth pcmk-1 pcmk-2
Username: hacluster
Password:
pcmk-1: Authorized
pcmk-2: Authorized

Next, use pcs cluster setup on the same node to generate and synchronize the corosync configuration:

[root@pcmk-1 ~]# pcs cluster setup --name mycluster pcmk-1 pcmk-2
Shutting down pacemaker/corosync services...
Redirecting to /bin/systemctl stop  pacemaker.service
Redirecting to /bin/systemctl stop  corosync.service
Killing any remaining services...
Removing all cluster configuration files...
pcmk-1: Succeeded
pcmk-2: Succeeded

If you received an authorization error for either of those commands, make sure you configured the hacluster user account on each node with the same password.

Note

Early versions of pcs required that --name be omitted from the above command.

If you are not using pcs for cluster administration, follow whatever procedures are appropriate for your tools to create a corosync.conf and copy it to all nodes.

The pcs command will configure corosync to use UDP unicast transport; if you choose to use multicast instead, choose a multicast address carefully. ^[4]

The final /etc/corosync.conf configuration on each node should look something like the sample in Appendix B, Sample Corosync Configuration.

^[4]For some subtle issues, see the now-defunct http://web.archive.org/web/20101211210054/http://29west.com/docs/THPM/multicast-address-assignment.html or the more detailed treatment in Cisco’s Guidelines for Enterprise IP Multicast Address Allocation paper.

Chapter 3. Pacemaker Tools

Table of Contents

3.1. Simplify administration using a cluster shell
3.2. Explore pcs

3.1. Simplify administration using a cluster shell

In the dark past, configuring Pacemaker required the administrator to read and write XML. In true UNIX style, there were also a number of different commands that specialized in different aspects of querying and updating the cluster.

All of that has been greatly simplified with the creation of unified command-line shells (and GUIs) that hide all the messy XML scaffolding.

These shells take all the individual aspects required for managing and configuring a cluster, and pack them into one simple-to-use command line tool.

They even allow you to queue up several changes at once and commit them atomically.

Two popular command-line shells are pcs and crmsh. This edition of Clusters from Scratch is based on pcs.

Note

The two shells share many concepts but the scope, layout and syntax does differ, so make sure you read the version of this guide that corresponds to the software installed on your system.

Important

Since pcs has the ability to manage all aspects of the cluster (both corosync and pacemaker), it requires a specific cluster stack to be in use: corosync 2.0 or later with votequorum plus Pacemaker 1.1.8 or later.

3.2. Explore pcs

Start by taking some time to familiarize yourself with what pcs can do.

[root@pcmk-1 ~]# pcs
Usage: pcs [-f file] [-h] [commands]...
Control and configure pacemaker and corosync.

Options:
    -h, --help  Display usage and exit
    -f file     Perform actions on file instead of active CIB
    --debug     Print all network traffic and external commands run
    --version   Print pcs version information

Commands:
    cluster     Configure cluster options and nodes
    resource    Manage cluster resources
    stonith     Configure fence devices
    constraint  Set resource constraints
    property    Set pacemaker properties
    acl         Set pacemaker access control lists
    status      View cluster status
    config      View and manage cluster configuration

As you can see, the different aspects of cluster management are separated into categories: resource, cluster, stonith, property, constraint, and status. To discover the functionality available in each of these categories, one can issue the command pcs category help. Below is an example of all the options available under the status category.

[root@pcmk-1 ~]# pcs status help
Usage: pcs status [commands]...
View current cluster and resource status
Commands:
    [status] [--full]
        View all information about the cluster and resources (--full provides
        more details)

    resources
        View current status of cluster resources

    groups
        View currently configured groups and their resources

    cluster
        View current cluster status

    corosync
        View current membership information as seen by corosync

    nodes [corosync|both|config]
        View current status of nodes from pacemaker. If 'corosync' is
        specified, print nodes currently configured in corosync, if 'both'
        is specified, print nodes from both corosync & pacemaker.  If 'config'
        is specified, print nodes from corosync & pacemaker configuration.

    pcsd <node> ...
        Show the current status of pcsd on the specified nodes

    xml
        View xml version of status (output from crm_mon -r -1 -X)

Additionally, if you are interested in the version and supported cluster stack(s) available with your Pacemaker installation, run:

[root@pcmk-1 ~]# pacemakerd --features
Pacemaker 1.1.12 (Build: a14efad)
 Supporting v3.0.9:  generated-manpages agent-manpages ascii-docs publican-docs ncurses libqb-logging libqb-ipc upstart systemd nagios  corosync-native atomic-attrd acls

Note

If the SNMP and/or email options are not listed, then Pacemaker was not built to support them. This may be by the choice of your distribution, or the required libraries may not have been available. Please contact whoever supplied you with the packages for more details.

Chapter 4. Start and Verify Cluster

Table of Contents

4.1. Start the Cluster
4.2. Verify Corosync Installation
4.3. Verify Pacemaker Installation

4.1. Start the Cluster

Now that corosync is configured, it is time to start the cluster. The command below will start corosync and pacemaker on both nodes in the cluster. If you are issuing the start command from a different node than the one you ran the pcs cluster auth command on earlier, you must authenticate on the current node you are logged into before you will be allowed to start the cluster.

[root@pcmk-1 ~]# pcs cluster start --all
pcmk-1: Starting Cluster...
pcmk-2: Starting Cluster...

Note

An alternative to using the pcs cluster start --all command is to issue either of the below command sequences on each node in the cluster separately:

# pcs cluster start
Starting Cluster...

# systemctl start corosync.service
# systemctl start pacemaker.service

Important

In this example, we are not enabling the corosync and pacemaker services to start at boot. If a cluster node fails or is rebooted, you will need to run pcs cluster start nodename (or --all) to start the cluster on it. While you could enable the services to start at boot, requiring a manual start of cluster services gives you the opportunity to do a post-mortem investigation of a node failure before returning it to the cluster.

4.2. Verify Corosync Installation

First, use corosync-cfgtool to check whether cluster communication is happy:

[root@pcmk-1 ~]# corosync-cfgtool -s
Printing ring status.
Local node ID 1
RING ID 0
        id      = 192.168.122.101
        status  = ring 0 active with no faults

We can see here that everything appears normal with our fixed IP address (not a 127.0.0.x loopback address) listed as the id, and no faults for the status.

If you see something different, you might want to start by checking the node’s network, firewall and selinux configurations.

Next, check the membership and quorum APIs:

[root@pcmk-1 ~]# corosync-cmapctl  | grep members
runtime.totem.pg.mrp.srp.members.1.config_version (u64) = 0
runtime.totem.pg.mrp.srp.members.1.ip (str) = r(0) ip(192.168.122.101)
runtime.totem.pg.mrp.srp.members.1.join_count (u32) = 1
runtime.totem.pg.mrp.srp.members.1.status (str) = joined
runtime.totem.pg.mrp.srp.members.2.config_version (u64) = 0
runtime.totem.pg.mrp.srp.members.2.ip (str) = r(0) ip(192.168.122.102)
runtime.totem.pg.mrp.srp.members.2.join_count (u32) = 2
runtime.totem.pg.mrp.srp.members.2.status (str) = joined

[root@pcmk-1 ~]# pcs status corosync
Membership information
 --------------------------
    Nodeid      Votes Name
         1          1 pcmk-1 (local)
         2          1 pcmk-2

You should see both nodes have joined the cluster.

4.3. Verify Pacemaker Installation

Now that we have confirmed that Corosync is functional, we can check the rest of the stack. Pacemaker has already been started, so verify the necessary processes are running:

[root@pcmk-1 ~]# ps axf
  PID TTY      STAT   TIME COMMAND
    2 ?        S      0:00 [kthreadd]
...lots of processes...
 1362 ?        Ssl    0:35 corosync
 1379 ?        Ss     0:00 /usr/sbin/pacemakerd -f
 1380 ?        Ss     0:00  \_ /usr/libexec/pacemaker/cib
 1381 ?        Ss     0:00  \_ /usr/libexec/pacemaker/stonithd
 1382 ?        Ss     0:00  \_ /usr/libexec/pacemaker/lrmd
 1383 ?        Ss     0:00  \_ /usr/libexec/pacemaker/attrd
 1384 ?        Ss     0:00  \_ /usr/libexec/pacemaker/pengine
 1385 ?        Ss     0:00  \_ /usr/libexec/pacemaker/crmd

If that looks OK, check the pcs status output:

[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
WARNING: no stonith devices and stonith-enabled is not false
Last updated: Tue Dec 16 16:15:29 2014
Last change: Tue Dec 16 15:49:47 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
0 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:


PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

Finally, ensure there are no startup errors (aside from messages relating to not having STONITH configured, which are OK at this point):

[root@pcmk-1 ~]# journalctl | grep -i error

Note

Other operating systems may report startup errors in other locations, for example /var/log/messages.

Repeat these checks on the other node. The results should be the same.

Chapter 5. Create an Active/Passive Cluster

Table of Contents

5.1. Explore the Existing Configuration
5.2. Add a Resource
5.3. Perform a Failover
5.4. Prevent Resources from Moving after Recovery

5.1. Explore the Existing Configuration

When Pacemaker starts up, it automatically records the number and details of the nodes in the cluster, as well as which stack is being used and the version of Pacemaker being used.

The first few lines of output should look like this:

[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
WARNING: no stonith devices and stonith-enabled is not false
Last updated: Tue Dec 16 16:15:29 2014
Last change: Tue Dec 16 15:49:47 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
0 Resources configured


Online: [ pcmk-1 pcmk-2 ]

For those who are not of afraid of XML, you can see the raw cluster configuration and status by using the pcs cluster cib command.

Example 5.1. The last XML you’ll see in this document

[root@pcmk-1 ~]# pcs cluster cib

<cib crm_feature_set="3.0.9" validate-with="pacemaker-2.3" epoch="5" num_updates="8" admin_epoch="0" cib-last-written="Tue Dec 16 15:49:47 2014" have-quorum="1" dc-uuid="2">
  <configuration>
    <crm_config>
      <cluster_property_set id="cib-bootstrap-options">
        <nvpair id="cib-bootstrap-options-have-watchdog" name="have-watchdog" value="false"/>
        <nvpair id="cib-bootstrap-options-dc-version" name="dc-version" value="1.1.12-a14efad"/>
        <nvpair id="cib-bootstrap-options-cluster-infrastructure" name="cluster-infrastructure" value="corosync"/>
        <nvpair id="cib-bootstrap-options-cluster-name" name="cluster-name" value="mycluster"/>
      </cluster_property_set>
    </crm_config>
    <nodes>
      <node id="1" uname="pcmk-1"/>
      <node id="2" uname="pcmk-2"/>
    </nodes>
    <resources/>
    <constraints/>
  </configuration>
  <status>
    <node_state id="2" uname="pcmk-2" in_ccm="true" crmd="online" crm-debug-origin="do_state_transition" join="member" expected="member">
      <lrm id="2">
        <lrm_resources/>
      </lrm>
      <transient_attributes id="2">
        <instance_attributes id="status-2">
          <nvpair id="status-2-shutdown" name="shutdown" value="0"/>
          <nvpair id="status-2-probe_complete" name="probe_complete" value="true"/>
        </instance_attributes>
      </transient_attributes>
    </node_state>
    <node_state id="1" uname="pcmk-1" in_ccm="true" crmd="online" crm-debug-origin="do_state_transition" join="member" expected="member">
      <lrm id="1">
        <lrm_resources/>
      </lrm>
      <transient_attributes id="1">
        <instance_attributes id="status-1">
          <nvpair id="status-1-shutdown" name="shutdown" value="0"/>
          <nvpair id="status-1-probe_complete" name="probe_complete" value="true"/>
        </instance_attributes>
      </transient_attributes>
    </node_state>
  </status>
</cib>

Before we make any changes, it’s a good idea to check the validity of the configuration.

[root@pcmk-1 ~]# crm_verify -L -V
   error: unpack_resources: Resource start-up disabled since no STONITH resources have been defined
   error: unpack_resources: Either configure some or disable STONITH with the stonith-enabled option
   error: unpack_resources: NOTE: Clusters with shared data need STONITH to ensure data integrity
Errors found during check: config not valid

As you can see, the tool has found some errors.

In order to guarantee the safety of your data, ^[5] the default for STONITH ^[6] in Pacemaker is enabled. However, it also knows when no STONITH configuration has been supplied and reports this as a problem (since the cluster would not be able to make progress if a situation requiring node fencing arose).

We will disable this feature for now and configure it later.

To disable STONITH, set the stonith-enabled cluster option to false:

[root@pcmk-1 ~]# pcs property set stonith-enabled=false
[root@pcmk-1 ~]# crm_verify -L

With the new cluster option set, the configuration is now valid.

Warning

The use of stonith-enabled=false is completely inappropriate for a production cluster. It tells the cluster to simply pretend that failed nodes are safely powered off. Some vendors will refuse to support clusters that have STONITH disabled.

We disable STONITH here only to defer the discussion of its configuration, which can differ widely from one installation to the next. See Section 8.1, “What is STONITH?” for information on why STONITH is important and details on how to configure it.

5.2. Add a Resource

Our first resource will be a unique IP address that the cluster can bring up on either node. Regardless of where any cluster service(s) are running, end users need a consistent address to contact them on. Here, I will choose 192.168.122.120 as the floating address, give it the imaginative name ClusterIP and tell the cluster to check whether it is running every 30 seconds.

Warning

The chosen address must not already be in use on the network. Do not reuse an IP address one of the nodes already has configured.

[root@pcmk-1 ~]# pcs resource create ClusterIP ocf:heartbeat:IPaddr2 \
    ip=192.168.122.120 cidr_netmask=32 op monitor interval=30s

Another important piece of information here is ocf:heartbeat:IPaddr2. This tells Pacemaker three things about the resource you want to add:

The first field (ocf in this case) is the standard to which the resource script conforms and where to find it.
The second field (heartbeat in this case) is standard-specific; for OCF resources, it tells the cluster which OCF namespace the resource script is in.
The third field (IPaddr2 in this case) is the name of the resource script.

To obtain a list of the available resource standards (the ocf part of ocf:heartbeat:IPaddr2), run:

[root@pcmk-1 ~]# pcs resource standards
ocf
lsb
service
systemd
stonith

To obtain a list of the available OCF resource providers (the heartbeat part of ocf:heartbeat:IPaddr2), run:

[root@pcmk-1 ~]# pcs resource providers
heartbeat
openstack
pacemaker

Finally, if you want to see all the resource agents available for a specific OCF provider (the IPaddr2 part of ocf:heartbeat:IPaddr2), run:

[root@pcmk-1 ~]# pcs resource agents ocf:heartbeat
CTDB
Delay
Dummy
Filesystem
IPaddr
IPaddr2
.
. (skipping lots of resources to save space)
.
rsyncd
slapd
symlink
tomcat

Now, verify that the IP resource has been added, and display the cluster’s status to see that it is now active:

[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Tue Dec 16 17:44:40 2014
Last change: Tue Dec 16 17:44:26 2014
Stack: corosync
Current DC: pcmk-1 (1) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
1 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-1

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

5.3. Perform a Failover

Since our ultimate goal is high availability, we should test failover of our new resource before moving on.

First, find the node on which the IP address is running.

[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Tue Dec 16 17:44:40 2014
Last change: Tue Dec 16 17:44:26 2014
Stack: corosync
Current DC: pcmk-1 (1) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
1 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-1

You can see that the status of the ClusterIP resource is Started on a particular node (in this example, pcmk-1). Shut down Pacemaker and Corosync on that machine to trigger a failover.

[root@pcmk-1 ~]# pcs cluster stop pcmk-1
Stopping Cluster...

Note

A cluster command such as pcs cluster stop nodename can be run from any node in the cluster, not just the affected node.

Verify that pacemaker and corosync are no longer running:

[root@pcmk-1 ~]# pcs status
Error: cluster is not currently running on this node

Go to the other node, and check the cluster status.

[root@pcmk-2 ~]# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 10:30:56 2014
Last change: Tue Dec 16 17:44:26 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
1 Resources configured


Online: [ pcmk-2 ]
OFFLINE: [ pcmk-1 ]

Full list of resources:

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-2

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

Notice that pcmk-1 is OFFLINE for cluster purposes (its PCSD is still Online, allowing it to receive pcs commands, but it is not participating in the cluster).

Also notice that ClusterIP is now running on pcmk-2 — failover happened automatically, and no errors are reported.

Quorum

If a cluster splits into two (or more) groups of nodes that can no longer communicate with each other (aka. partitions), quorum is used to prevent resources from starting on more nodes than desired, which would risk data corruption.

A cluster has quorum when more than half of all known nodes are online in the same partition, or for the mathematically inclined, whenever the following equation is true:

total_nodes < 2 * active_nodes

For example, if a 5-node cluster split into 3- and 2-node paritions, the 3-node partition would have quorum and could continue serving resources. If a 6-node cluster split into two 3-node partitions, neither partition would have quorum; pacemaker’s default behavior in such cases is to stop all resources, in order to prevent data corruption.

Two-node clusters are a special case. By the above definition, a two-node cluster would only have quorum when both nodes are running. This would make the creation of a two-node cluster pointless, ^[7] but corosync has the ability to treat two-node clusters as if only one node is required for quorum.

The pcs cluster setup command will automatically configure two_node: 1 in corosync.conf, so a two-node cluster will "just work".

If you are using a different cluster shell, you will have to configure corosync.conf appropriately yourself. If you are using older versions of corosync, you will have to ignore quorum at the pacemaker level, using pcs property set no-quorum-policy=ignore (or the equivalent command if you are using a different cluster shell).

Now, simulate node recovery by restarting the cluster stack on pcmk-1, and check the cluster’s status. (It may take a little while before the cluster gets going on the node, but it eventually will look like the below.)

[root@pcmk-1 ~]# pcs cluster start pcmk-1
pcmk-1: Starting Cluster...
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 10:50:11 2014
Last change: Tue Dec 16 17:44:26 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
1 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-2

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

Note

With older versions of pacemaker, the cluster might move the IP back to its original location (pcmk-1). Usually, this is no longer the case.

5.4. Prevent Resources from Moving after Recovery

In most circumstances, it is highly desirable to prevent healthy resources from being moved around the cluster. Moving resources almost always requires a period of downtime. For complex services such as databases, this period can be quite long.

To address this, Pacemaker has the concept of resource stickiness, which controls how strongly a service prefers to stay running where it is. You may like to think of it as the "cost" of any downtime. By default, Pacemaker assumes there is zero cost associated with moving resources and will do so to achieve "optimal" ^[8] resource placement. We can specify a different stickiness for every resource, but it is often sufficient to change the default.

[root@pcmk-1 ~]# pcs resource defaults resource-stickiness=100
[root@pcmk-1 ~]# pcs resource defaults
resource-stickiness: 100

Note

Older versions of pcs required that rsc be added after resource in the above commands.

^[5]If the data is corrupt, there is little point in continuing to make it available

^[6]A common node fencing mechanism. Used to ensure data integrity by powering off "bad" nodes

^[7]Some would argue that two-node clusters are always pointless, but that is an argument for another time

^[8]Pacemaker’s definition of optimal may not always agree with that of a human’s. The order in which Pacemaker processes lists of resources and nodes creates implicit preferences in situations where the administrator has not explicitly specified them.

Chapter 6. Add Apache as a Cluster Service

Table of Contents

6.1. Install Apache
6.2. Create Website Documents
6.3. Enable the Apache status URL
6.4. Configure the Cluster
6.5. Ensure Resources Run on the Same Host
6.6. Ensure Resources Start and Stop in Order
6.7. Prefer One Node Over Another
6.8. Move Resources Manually

Now that we have a basic but functional active/passive two-node cluster, we’re ready to add some real services. We’re going to start with Apache because it is a feature of many clusters and relatively simple to configure.

6.1. Install Apache

Before continuing, we need to make sure Apache is installed on both hosts. We also need the wget tool in order for the cluster to be able to check the status of the Apache server.

# yum install -y httpd wget
# firewall-cmd --permanent --add-service=http
# firewall-cmd --reload

Important

Do not enable the httpd service. Services that are intended to be managed via the cluster software should never be managed by the OS.

It is often useful, however, to manually start the service, verify that it works, then stop it again, before adding it to the cluster. This allows you to resolve any non-cluster-related problems before continuing. Since this is a simple example, we’ll skip that step here.

6.2. Create Website Documents

We need to create a page for Apache to serve. On CentOS 7.1, the default Apache document root is /var/www/html, so we’ll create an index file there. For the moment, we will simplify things by serving a static site and manually synchronizing the data between the two nodes, so run this command on both nodes:

# cat <<-END >/var/www/html/index.html
 <html>
 <body>My Test Site - $(hostname)</body>
 </html>
END

6.3. Enable the Apache status URL

In order to monitor the health of your Apache instance, and recover it if it fails, the resource agent used by Pacemaker assumes the server-status URL is available. On both nodes, enable the URL with:

# cat <<-END >/etc/httpd/conf.d/status.conf
 <Location /server-status>
    SetHandler server-status
    Order deny,allow
    Deny from all
    Allow from 127.0.0.1
 </Location>
END

Note

If you are using a different operating system, server-status may already be enabled or may be configurable in a different location.

6.4. Configure the Cluster

At this point, Apache is ready to go, and all that needs to be done is to add it to the cluster. Let’s call the resource WebSite. We need to use an OCF resource script called apache in the heartbeat namespace. ^[9] The script’s only required parameter is the path to the main Apache configuration file, and we’ll tell the cluster to check once a minute that Apache is still running.

[root@pcmk-1 ~]# pcs resource create WebSite ocf:heartbeat:apache  \
      configfile=/etc/httpd/conf/httpd.conf \
      statusurl="http://localhost/server-status" \
      op monitor interval=1min

By default, the operation timeout for all resources' start, stop, and monitor operations is 20 seconds. In many cases, this timeout period is less than a particular resource’s advised timeout period. For the purposes of this tutorial, we will adjust the global operation timeout default to 240 seconds.

[root@pcmk-1 ~]# pcs resource op defaults timeout=240s
[root@pcmk-1 ~]# pcs resource op defaults
timeout: 240s

Note

In a production cluster, it is usually better to adjust each resource’s start, stop, and monitor timeouts to values that are appropriate to the behavior observed in your environment, rather than adjust the global default.

After a short delay, we should see the cluster start Apache.

[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 12:40:41 2014
Last change: Wed Dec 17 12:40:05 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
2 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-2
 WebSite        (ocf::heartbeat:apache):        Started pcmk-1

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

Wait a moment, the WebSite resource isn’t running on the same host as our IP address!

Note

If, in the pcs status output, you see the WebSite resource has failed to start, then you’ve likely not enabled the status URL correctly. You can check whether this is the problem by running:

wget -O - http://127.0.0.1/server-status

If you see Connection refused in the output, then this is likely the problem. Ensure that Allow from 127.0.0.1 is present for the <Location /server-status> block.

6.5. Ensure Resources Run on the Same Host

To reduce the load on any one machine, Pacemaker will generally try to spread the configured resources across the cluster nodes. However, we can tell the cluster that two resources are related and need to run on the same host (or not at all). Here, we instruct the cluster that WebSite can only run on the host that ClusterIP is active on.

To achieve this, we use a colocation constraint that indicates it is mandatory for WebSite to run on the same node as ClusterIP. The "mandatory" part of the colocation constraint is indicated by using a score of INFINITY. The INFINITY score also means that if ClusterIP is not active anywhere, WebSite will not be permitted to run.

Note

If ClusterIP is not active anywhere, WebSite will not be permitted to run anywhere.

Important

Colocation constraints are "directional", in that they imply certain things about the order in which the two resources will have a location chosen. In this case, we’re saying that WebSite needs to be placed on the same machine as ClusterIP, which implies that the cluster must know the location of ClusterIP before choosing a location for WebSite.

[root@pcmk-1 ~]# pcs constraint colocation add WebSite with ClusterIP INFINITY
[root@pcmk-1 ~]# pcs constraint
Location Constraints:
Ordering Constraints:
Colocation Constraints:
  WebSite with ClusterIP (score:INFINITY)
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 13:57:58 2014
Last change: Wed Dec 17 13:57:22 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
2 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-2
 WebSite        (ocf::heartbeat:apache):        Started pcmk-2

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

6.6. Ensure Resources Start and Stop in Order

Like many services, Apache can be configured to bind to specific IP addresses on a host or to the wildcard IP address. If Apache binds to the wildcard, it doesn’t matter whether an IP address is added before or after Apache starts; Apache will respond on that IP just the same. However, if Apache binds only to certain IP address(es), the order matters: If the address is added after Apache starts, Apache won’t respond on that address.

To be sure our WebSite responds regardless of Apache’s address configuration, we need to make sure ClusterIP not only runs on the same node, but starts before WebSite. A colocation constraint only ensures the resources run together, not the order in which they are started and stopped.

We do this by adding an ordering constraint. By default, all order constraints are mandatory, which means that the recovery of ClusterIP will also trigger the recovery of WebSite.

[root@pcmk-1 ~]# pcs constraint order ClusterIP then WebSite
Adding ClusterIP WebSite (kind: Mandatory) (Options: first-action=start then-action=start)
[root@pcmk-1 ~]# pcs constraint
Location Constraints:
Ordering Constraints:
  start ClusterIP then start WebSite (kind:Mandatory)
Colocation Constraints:
  WebSite with ClusterIP (score:INFINITY)

6.7. Prefer One Node Over Another

Pacemaker does not rely on any sort of hardware symmetry between nodes, so it may well be that one machine is more powerful than the other. In such cases, it makes sense to host the resources on the more powerful node if it is available. To do this, we create a location constraint.

In the location constraint below, we are saying the WebSite resource prefers the node pcmk-1 with a score of 50. Here, the score indicates how badly we’d like the resource to run at this location.

[root@pcmk-1 ~]# pcs constraint location WebSite prefers pcmk-1=50
[root@pcmk-1 ~]# pcs constraint
Location Constraints:
  Resource: WebSite
    Enabled on: pcmk-1 (score:50)
Ordering Constraints:
  start ClusterIP then start WebSite (kind:Mandatory)
Colocation Constraints:
  WebSite with ClusterIP (score:INFINITY)
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 14:11:49 2014
Last change: Wed Dec 17 14:11:20 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
2 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-2
 WebSite        (ocf::heartbeat:apache):        Started pcmk-2

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

Wait a minute, the resources are still on pcmk-2!

Even though WebSite now prefers to run on pcmk-1, that preference is (intentionally) less than the resource stickiness (how much we preferred not to have unnecessary downtime).

To see the current placement scores, you can use a tool called crm_simulate.

[root@pcmk-1 ~]# crm_simulate -sL

Current cluster status:
Online: [ pcmk-1 pcmk-2 ]

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-2
 WebSite        (ocf::heartbeat:apache):        Started pcmk-2

Allocation scores:
native_color: ClusterIP allocation score on pcmk-1: 50
native_color: ClusterIP allocation score on pcmk-2: 200
native_color: WebSite allocation score on pcmk-1: -INFINITY
native_color: WebSite allocation score on pcmk-2: 100

Transition Summary:

6.8. Move Resources Manually

There are always times when an administrator needs to override the cluster and force resources to move to a specific location. In this example, we will force the WebSite to move to pcmk-1 by updating our previous location constraint with a score of INFINITY.

[root@pcmk-1 ~]# pcs constraint location WebSite prefers pcmk-1=INFINITY
[root@pcmk-1 ~]# pcs constraint
Location Constraints:
  Resource: WebSite
    Enabled on: pcmk-1 (score:INFINITY)
Ordering Constraints:
  start ClusterIP then start WebSite (kind:Mandatory)
Colocation Constraints:
  WebSite with ClusterIP (score:INFINITY)
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 14:19:34 2014
Last change: Wed Dec 17 14:18:37 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
2 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-1
 WebSite        (ocf::heartbeat:apache):        Started pcmk-1

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

Once we’ve finished whatever activity required us to move the resources to pcmk-1 (in our case nothing), we can then allow the cluster to resume normal operation by removing the new constraint. Since we previously configured a default stickiness, the resources will remain on pcmk-1.

First, use the --full option to get the constraint’s ID:

[root@pcmk-1 ~]# pcs constraint --full
Location Constraints:
  Resource: WebSite
    Enabled on: pcmk-1 (score:INFINITY) (id:location-WebSite-pcmk-1-INFINITY)
Ordering Constraints:
  start ClusterIP then start WebSite (kind:Mandatory) (id:order-ClusterIP-WebSite-mandatory)
Colocation Constraints:
  WebSite with ClusterIP (score:INFINITY) (id:colocation-WebSite-ClusterIP-INFINITY)

Then remove the desired contraint using its ID:

[root@pcmk-1 ~]# pcs constraint remove location-WebSite-pcmk-1-INFINITY
[root@pcmk-1 ~]# pcs constraint
Location Constraints:
Ordering Constraints:
  start ClusterIP then start WebSite (kind:Mandatory)
Colocation Constraints:
  WebSite with ClusterIP (score:INFINITY)

Note that the location constraint is now gone. If we check the cluster status, we can also see that (as expected) the resources are still active on pcmk-1.

# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 14:25:21 2014
Last change: Wed Dec 17 14:24:29 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
2 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-1
 WebSite        (ocf::heartbeat:apache):        Started pcmk-1

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

^[9]Compare the key used here, ocf:heartbeat:apache, with the one we used earlier for the IP address, ocf:heartbeat:IPaddr2

Chapter 7. Replicate Storage Using DRBD

Table of Contents

7.1. Install the DRBD Packages
7.2. Allocate a Disk Volume for DRBD
7.3. Configure DRBD
7.4. Initialize DRBD
7.5. Populate the DRBD Disk
7.6. Configure the Cluster for the DRBD device
7.7. Configure the Cluster for the Filesystem
7.8. Test Cluster Failover

Even if you’re serving up static websites, having to manually synchronize the contents of that website to all the machines in the cluster is not ideal. For dynamic websites, such as a wiki, it’s not even an option. Not everyone care afford network-attached storage, but somehow the data needs to be kept in sync.

Enter DRBD, which can be thought of as network-based RAID-1. ^[10]

7.1. Install the DRBD Packages

DRBD itself is included in the upstream kernel,^[11] but we do need some utilities to use it effectively.

CentOS does not ship these utilities, so we need to enable a third-party repository to get them. Supported packages for many OSes are available from DRBD’s maker LINBIT, but here we’ll use the free ELRepo repository.

On both nodes, import the ELRepo package signing key, and enable the repository:

# rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
# rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-2.el7.elrepo.noarch.rpm

Now, we can install the DRBD kernel module and utilities:

# yum install -y kmod-drbd84 drbd84-utils

Important

The version of drbd84-utils shipped with CentOS 7.1 has a bug in the Pacemaker integration script. Until a fix is packaged, download the affected script directly from the upstream, on both nodes:

# curl -o /usr/lib/ocf/resource.d/linbit/drbd 'http://git.linbit.com/gitweb.cgi?p=drbd-utils.git;a=blob_plain;f=scripts/drbd.ocf;h=cf6b966341377a993d1bf5f585a5b9fe72eaa5f2;hb=c11ba026bbbbc647b8112543df142f2185cb4b4b'

This is a temporary fix that will be overwritten if the package is upgraded.

DRBD will not be able to run under the default SELinux security policies. If you are familiar with SELinux, you can modify the policies in a more fine-grained manner, but here we will simply exempt DRBD processes from SELinux control:

# semanage permissive -a drbd_t

We will configure DRBD to use port 7789, so allow that port from each host to the other:

[root@pcmk-1 ~]# firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="192.168.122.102" port port="7789" protocol="tcp" accept'
success
[root@pcmk-1 ~]# firewall-cmd --reload
success

[root@pcmk-2 ~]# firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="192.168.122.101" port port="7789" protocol="tcp" accept'
success
[root@pcmk-2 ~]# firewall-cmd --reload
success

Note

In this example, we have only two nodes, and all network traffic is on the same LAN. In production, it is recommended to use a dedicated, isolated network for cluster-related traffic, so the firewall configuration would likely be different; one approach would be to add the dedicated network interfaces to the trusted zone.

7.2. Allocate a Disk Volume for DRBD

DRBD will need its own block device on each node. This can be a physical disk partition or logical volume, of whatever size you need for your data. For this document, we will use a 1GiB logical volume, which is more than sufficient for a single HTML file and (later) GFS2 metadata.

[root@pcmk-1 ~]# vgdisplay | grep -e Name -e Free
  VG Name               centos_pcmk-1
  Free  PE / Size       382 / 1.49 GiB
[root@pcmk-1 ~]# lvcreate --name drbd-demo --size 1G centos_pcmk-1
Logical volume "drbd-demo" created
[root@pcmk-1 ~]# lvs
  LV        VG            Attr       LSize Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  drbd-demo centos_pcmk-1 -wi-a----- 1.00g
  root      centos_pcmk-1 -wi-ao---- 5.00g
  swap      centos_pcmk-1 -wi-ao---- 1.00g

Repeat for the second node, making sure to use the same size:

[root@pcmk-1 ~]# ssh pcmk-2 -- lvcreate --name drbd-demo --size 1G centos_pcmk-2
Logical volume "drbd-demo" created

7.3. Configure DRBD

There is no series of commands for building a DRBD configuration, so simply run this on both nodes to use this sample configuration:

# cat <<END >/etc/drbd.d/wwwdata.res
resource wwwdata {
 protocol C;
 meta-disk internal;
 device /dev/drbd1;
 syncer {
  verify-alg sha1;
 }
 net {
  allow-two-primaries;
 }
 on pcmk-1 {
  disk   /dev/centos_pcmk-1/drbd-demo;
  address  192.168.122.101:7789;
 }
 on pcmk-2 {
  disk   /dev/centos_pcmk-2/drbd-demo;
  address  192.168.122.102:7789;
 }
}
END

Important

Edit the file to use the hostnames, IP addresses and logical volume paths of your nodes if they differ from the ones used in this guide.

Note

Detailed information on the directives used in this configuration (and other alternatives) is available at http://www.drbd.org/users-guide/ch-configure.html

The allow-two-primaries option would not normally be used in an active/passive cluster. We are adding it here for the convenience of changing to an active/active cluster later.

7.4. Initialize DRBD

With the configuration in place, we can now get DRBD running.

These commands create the local metadata for the DRBD resource, ensure the DRBD kernel module is loaded, and bring up the DRBD resource. Run them on one node:

[root@pcmk-1 ~]# drbdadm create-md wwwdata
initializing activity log
NOT initializing bitmap
Writing meta data...
New drbd meta data block successfully created.
[root@pcmk-1 ~]# modprobe drbd
[root@pcmk-1 ~]# drbdadm up wwwdata

We can confirm DRBD’s status on this node:

[root@pcmk-1 ~]# cat /proc/drbd
version: 8.4.6 (api:1/proto:86-101)
GIT-hash: 833d830e0152d1e457fa7856e71e11248ccf3f70 build by phil@Build64R7, 2015-04-10 05:13:52

 1: cs:WFConnection ro:Secondary/Unknown ds:Inconsistent/DUnknown C r----s
    ns:0 nr:0 dw:0 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:1048508

Because we have not yet initialized the data, this node’s data is marked as Inconsistent. Because we have not yet initialized the second node, the local state is WFConnection (waiting for connection), and the partner node’s status is marked as Unknown.

Now, repeat the above commands on the second node. This time, when we check the status, it shows:

[root@pcmk-2 ~]# cat /proc/drbd
version: 8.4.6 (api:1/proto:86-101)
GIT-hash: 833d830e0152d1e457fa7856e71e11248ccf3f70 build by phil@Build64R7, 2015-04-10 05:13:52

 1: cs:Connected ro:Secondary/Secondary ds:Inconsistent/Inconsistent C r-----
    ns:0 nr:0 dw:0 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:1048508

You can see the state has changed to Connected, meaning the two DRBD nodes are communicating properly, and both nodes are in Secondary role with Inconsistent data.

To make the data consistent, we need to tell DRBD which node should be considered to have the correct data. In this case, since we are creating a new resource, both have garbage, so we’ll just pick pcmk-1 and run this command on it:

[root@pcmk-1 ~]# drbdadm primary --force wwwdata

Note

If you are using an older version of DRBD, the required syntax may be different. See the documentation for your version for how to perform these commands.

If we check the status immediately, we’ll see something like this:

[root@pcmk-1 ~]# cat /proc/drbd
version: 8.4.6 (api:1/proto:86-101)
GIT-hash: 833d830e0152d1e457fa7856e71e11248ccf3f70 build by phil@Build64R7, 2015-04-10 05:13:52

 1: cs:SyncSource ro:Primary/Secondary ds:UpToDate/Inconsistent C r-----
    ns:2872 nr:0 dw:0 dr:3784 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:1045636
        [>....................] sync'ed:  0.4% (1045636/1048508)K
        finish: 0:10:53 speed: 1,436 (1,436) K/sec

We can see that this node has the Primary role, the partner node has the Secondary role, this node’s data is now considered UpToDate, the partner node’s data is still Inconsistent, and a progress bar shows how far along the partner node is in synchronizing the data.

After a while, the sync should finish, and you’ll see something like:

[root@pcmk-1 ~]# cat /proc/drbd
version: 8.4.6 (api:1/proto:86-101)
GIT-hash: 833d830e0152d1e457fa7856e71e11248ccf3f70 build by phil@Build64R7, 2015-04-10 05:13:52

 1: cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate C r-----
    ns:1048508 nr:0 dw:0 dr:1049420 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:0

Both sets of data are now UpToDate, and we can proceed to creating and populating a filesystem for our WebSite resource’s documents.

7.5. Populate the DRBD Disk

On the node with the primary role (pcmk-1 in this example), create a filesystem on the DRBD device:

[root@pcmk-1 ~]# mkfs.xfs /dev/drbd1
meta-data=/dev/drbd1             isize=256    agcount=4, agsize=65532 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=0        finobt=0
data     =                       bsize=4096   blocks=262127, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
log      =internal log           bsize=4096   blocks=853, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

Note

In this example, we create an xfs filesystem with no special options. In a production environment, you should choose a filesystem type and options that are suitable for your application.

Mount the newly created filesystem, populate it with our web document, give it the same SELinux policy as the web document root, then unmount it (the cluster will handle mounting and unmounting it later):

[root@pcmk-1 ~]# mount /dev/drbd1 /mnt
[root@pcmk-1 ~]# cat <<-END >/mnt/index.html
 <html>
  <body>My Test Site - DRBD</body>
 </html>
END
[root@pcmk-1 ~]# chcon -R --reference=/var/www/html /mnt
[root@pcmk-1 ~]# umount /dev/drbd1

7.6. Configure the Cluster for the DRBD device

One handy feature pcs has is the ability to queue up several changes into a file and commit those changes atomically. To do this, start by populating the file with the current raw XML config from the CIB.

[root@pcmk-1 ~]# pcs cluster cib drbd_cfg

Using the pcs -f option, make changes to the configuration saved in the drbd_cfg file. These changes will not be seen by the cluster until the drbd_cfg file is pushed into the live cluster’s CIB later.

Here, we create a cluster resource for the DRBD device, and an additional clone resource to allow the resource to run on both nodes at the same time.

[root@pcmk-1 ~]# pcs -f drbd_cfg resource create WebData ocf:linbit:drbd \
         drbd_resource=wwwdata op monitor interval=60s
[root@pcmk-1 ~]# pcs -f drbd_cfg resource master WebDataClone WebData \
         master-max=1 master-node-max=1 clone-max=2 clone-node-max=1 \
         notify=true
[root@pcmk-1 ~]# pcs -f drbd_cfg resource show
 ClusterIP      (ocf::heartbeat:IPaddr2):       Started
 WebSite        (ocf::heartbeat:apache):        Started
 Master/Slave Set: WebDataClone [WebData]
     Stopped: [ pcmk-1 pcmk-2 ]

After you are satisfied with all the changes, you can commit them all at once by pushing the drbd_cfg file into the live CIB.

[root@pcmk-1 ~]# pcs cluster cib-push drbd_cfg
CIB updated

Note

Early versions of pcs required push cib in place of cib-push above.

Let’s see what the cluster did with the new configuration:

[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Fri Aug 14 09:29:41 2015
Last change: Fri Aug 14 09:29:25 2015
Stack: corosync
Current DC: pcmk-1 (1) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
4 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-1
 WebSite        (ocf::heartbeat:apache):        Started pcmk-1
 Master/Slave Set: WebDataClone [WebData]
     Masters: [ pcmk-1 ]
     Slaves: [ pcmk-2 ]

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

We can see that WebDataClone (our DRBD device) is running as master (DRBD’s primary role) on pcmk-1 and slave (DRBD’s secondary role) on pcmk-2.

Important

The resource agent should load the DRBD module when needed if it’s not already loaded. If that does not happen, configure your operating system to load the module at boot time. For CentOS 7.1, you would run this on both nodes:

# echo drbd >/etc/modules-load.d/drbd.conf

7.7. Configure the Cluster for the Filesystem

Now that we have a working DRBD device, we need to mount its filesystem.

In addition to defining the filesystem, we also need to tell the cluster where it can be located (only on the DRBD Primary) and when it is allowed to start (after the Primary was promoted).

We are going to take a shortcut when creating the resource this time. Instead of explicitly saying we want the ocf:heartbeat:Filesystem script, we are only going to ask for Filesystem. We can do this because we know there is only one resource script named Filesystem available to pacemaker, and that pcs is smart enough to fill in the ocf:heartbeat: portion for us correctly in the configuration. If there were multiple Filesystem scripts from different OCF providers, we would need to specify the exact one we wanted.

Once again, we will queue our changes to a file and then push the new configuration to the cluster as the final step.

[root@pcmk-1 ~]# pcs cluster cib fs_cfg
[root@pcmk-1 ~]# pcs -f fs_cfg resource create WebFS Filesystem \
         device="/dev/drbd1" directory="/var/www/html" fstype="xfs"
[root@pcmk-1 ~]# pcs -f fs_cfg constraint colocation add WebFS with WebDataClone INFINITY with-rsc-role=Master
[root@pcmk-1 ~]# pcs -f fs_cfg constraint order promote WebDataClone then start WebFS
Adding WebDataClone WebFS (kind: Mandatory) (Options: first-action=promote then-action=start)

We also need to tell the cluster that Apache needs to run on the same machine as the filesystem and that it must be active before Apache can start.

[root@pcmk-1 ~]# pcs -f fs_cfg constraint colocation add WebSite with WebFS INFINITY
[root@pcmk-1 ~]# pcs -f fs_cfg constraint order WebFS then WebSite
Adding WebFS WebSite (kind: Mandatory) (Options: first-action=start then-action=start)

Review the updated configuration.

[root@pcmk-1 ~]# pcs -f fs_cfg constraint
Location Constraints:
Ordering Constraints:
  start ClusterIP then start WebSite (kind:Mandatory)
  promote WebDataClone then start WebFS (kind:Mandatory)
  start WebFS then start WebSite (kind:Mandatory)
Colocation Constraints:
  WebSite with ClusterIP (score:INFINITY)
  WebFS with WebDataClone (score:INFINITY) (with-rsc-role:Master)
  WebSite with WebFS (score:INFINITY)

[root@pcmk-1 ~]# pcs -f fs_cfg resource show
 ClusterIP      (ocf::heartbeat:IPaddr2):       Started
 WebSite        (ocf::heartbeat:apache):        Started
 Master/Slave Set: WebDataClone [WebData]
     Masters: [ pcmk-1 ]
     Slaves: [ pcmk-2 ]
 WebFS  (ocf::heartbeat:Filesystem):    Stopped

After reviewing the new configuration, upload it and watch the cluster put it into effect.

[root@pcmk-1 ~]# pcs cluster cib-push fs_cfg
[root@pcmk-1 ~]# pcs status
Last updated: Fri Aug 14 09:34:11 2015
Last change: Fri Aug 14 09:34:09 2015
Stack: corosync
Current DC: pcmk-1 (1) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
5 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-1
 WebSite        (ocf::heartbeat:apache):        Started pcmk-1
 Master/Slave Set: WebDataClone [WebData]
     Masters: [ pcmk-1 ]
     Slaves: [ pcmk-2 ]
 WebFS  (ocf::heartbeat:Filesystem):    Started pcmk-1

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

7.8. Test Cluster Failover

Previously, we used pcs cluster stop pcmk-1 to stop all cluster services on pcmk-1, failing over the cluster resources, but there is another way to safely simulate node failure.

We can put the node into standby mode. Nodes in this state continue to run corosync and pacemaker but are not allowed to run resources. Any resources found active there will be moved elsewhere. This feature can be particularly useful when performing system administration tasks such as updating packages used by cluster resources.

Put the active node into standby mode, and observe the cluster move all the resources to the other node. The node’s status will change to indicate that it can no longer host resources.

[root@pcmk-1 ~]# pcs cluster standby pcmk-1
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Fri Aug 14 09:36:49 2015
Last change: Fri Aug 14 09:36:43 2015
Stack: corosync
Current DC: pcmk-1 (1) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
5 Resources configured


Node pcmk-1 (1): standby
Online: [ pcmk-2 ]

Full list of resources:

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-2
 WebSite        (ocf::heartbeat:apache):        Started pcmk-2
 Master/Slave Set: WebDataClone [WebData]
     Masters: [ pcmk-2 ]
     Stopped: [ pcmk-1 ]
 WebFS  (ocf::heartbeat:Filesystem):    Started pcmk-2

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

Once we’ve done everything we needed to on pcmk-1 (in this case nothing, we just wanted to see the resources move), we can allow the node to be a full cluster member again.

[root@pcmk-1 ~]# pcs cluster unstandby pcmk-1
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Fri Aug 14 09:38:02 2015
Last change: Fri Aug 14 09:37:56 2015
Stack: corosync
Current DC: pcmk-1 (1) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
5 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-2
 WebSite        (ocf::heartbeat:apache):        Started pcmk-2
 Master/Slave Set: WebDataClone [WebData]
     Masters: [ pcmk-2 ]
     Slaves: [ pcmk-1 ]
 WebFS  (ocf::heartbeat:Filesystem):    Started pcmk-2

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

Notice that pcmk-1 is back to the Online state, and that the cluster resources stay where they are due to our resource stickiness settings configured earlier.

^[10]See http://www.drbd.org/ for details.

^[11]Since version 2.6.33

Chapter 8. Configure STONITH

Table of Contents

8.1. What is STONITH?
8.2. Choose a STONITH Device
8.3. Configure the Cluster for STONITH
8.4. Example

8.1. What is STONITH?

STONITH (Shoot The Other Node In The Head aka. fencing) protects your data from being corrupted by rogue nodes or unintended concurrent access.

Just because a node is unresponsive doesn’t mean it has stopped accessing your data. The only way to be 100% sure that your data is safe, is to use STONITH to ensure that the node is truly offline before allowing the data to be accessed from another node.

STONITH also has a role to play in the event that a clustered service cannot be stopped. In this case, the cluster uses STONITH to force the whole node offline, thereby making it safe to start the service elsewhere.

8.2. Choose a STONITH Device

It is crucial that your STONITH device can allow the cluster to differentiate between a node failure and a network failure.

A common mistake people make when choosing a STONITH device is to use a remote power switch (such as many on-board IPMI controllers) that shares power with the node it controls. If the power fails in such a case, the cluster cannot be sure whether the node is really offline, or active and suffering from a network fault, so the cluster will stop all resources to avoid a possible split-brain situation.

Likewise, any device that relies on the machine being active (such as SSH-based "devices" sometimes used during testing) is inappropriate.

8.3. Configure the Cluster for STONITH

Install the STONITH agent(s). To see what packages are available, run yum search fence-. Be sure to install the package(s) on all cluster nodes.
Configure the STONITH device itself to be able to fence your nodes and accept fencing requests. This includes any necessary configuration on the device and on the nodes, and any firewall or SELinux changes needed. Test the communication between the device and your nodes.
Find the correct STONITH agent script: pcs stonith list
Find the parameters associated with the device: pcs stonith describe agent_name
Create a local copy of the CIB: pcs cluster cib stonith_cfg
Create the fencing resource: pcs -f stonith_cfg stonith create stonith_id stonith_device_type [stonith_device_options]

Any flags that do not take arguments, such as --ssl, should be passed as ssl=1.
Enable STONITH in the cluster: pcs -f stonith_cfg property set stonith-enabled=true
If the device does not know how to fence nodes based on their uname, you may also need to set the special pcmk_host_map parameter. See man stonithd for details.
If the device does not support the list command, you may also need to set the special pcmk_host_list and/or pcmk_host_check parameters. See man stonithd for details.
If the device does not expect the victim to be specified with the port parameter, you may also need to set the special pcmk_host_argument parameter. See man stonithd for details.
Commit the new configuration: pcs cluster cib-push stonith_cfg
Once the STONITH resource is running, test it (you might want to stop the cluster on that machine first): stonith_admin --reboot nodename

8.4. Example

For this example, assume we have a chassis containing four nodes and an IPMI device active on 10.0.0.1. Following the steps above would go something like this:

Step 1: Install the fence-agents-ipmilan package on both nodes.

Step 2: Configure the IP address, authentication credentials, etc. in the IPMI device itself.

Step 3: Choose the fence_ipmilan STONITH agent.

Step 4: Obtain the agent’s possible parameters:

[root@pcmk-1 ~]# pcs stonith describe fence_ipmilan
Stonith options for: fence_ipmilan
  ipport: TCP/UDP port to use for connection with device
  inet6_only: Forces agent to use IPv6 addresses only
  ipaddr (required): IP Address or Hostname
  passwd_script: Script to retrieve password
  method: Method to fence (onoff|cycle)
  inet4_only: Forces agent to use IPv4 addresses only
  passwd: Login password or passphrase
  lanplus: Use Lanplus to improve security of connection
  auth: IPMI Lan Auth type.
  cipher: Ciphersuite to use (same as ipmitool -C parameter)
  privlvl: Privilege level on IPMI device
  action (required): Fencing Action
  login: Login Name
  verbose: Verbose mode
  debug: Write debug information to given file
  version: Display version information and exit
  help: Display help and exit
  power_wait: Wait X seconds after issuing ON/OFF
  login_timeout: Wait X seconds for cmd prompt after login
  power_timeout: Test X seconds for status change after ON/OFF
  delay: Wait X seconds before fencing is started
  ipmitool_path: Path to ipmitool binary
  shell_timeout: Wait X seconds for cmd prompt after issuing command
  retry_on: Count of attempts to retry power on
  sudo: Use sudo (without password) when calling 3rd party sotfware.
  stonith-timeout: How long to wait for the STONITH action (reboot, on, off) to complete per a stonith device.
  priority: The priority of the stonith resource. Devices are tried in order of highest priority to lowest.
  pcmk_host_map: A mapping of host names to ports numbers for devices that do not support host names.
  pcmk_host_list: A list of machines controlled by this device (Optional unless pcmk_host_check=static-list).
  pcmk_host_check: How to determine which machines are controlled by the device.

Step 5: pcs cluster cib stonith_cfg

Step 6: Here are example parameters for creating our STONITH resource:

[root@pcmk-1 ~]# pcs -f stonith_cfg stonith create ipmi-fencing fence_ipmilan \
      pcmk_host_list="pcmk-1 pcmk-2" ipaddr=10.0.0.1 login=testuser \
      passwd=acd123 op monitor interval=60s
[root@pcmk-1 ~]# pcs -f stonith_cfg stonith
 ipmi-fencing   (stonith:fence_ipmilan):        Stopped

Steps 7-10: Enable STONITH in the cluster:

[root@pcmk-1 ~]# pcs -f stonith_cfg property set stonith-enabled=true
[root@pcmk-1 ~]# pcs -f stonith_cfg property
Cluster Properties:
 cluster-infrastructure: corosync
 cluster-name: mycluster
 dc-version: 1.1.12-a14efad
 have-watchdog: false
 stonith-enabled: true

Step 11: pcs cluster cib-push stonith_cfg

Step 12: Test:

[root@pcmk-1 ~]# pcs cluster stop pcmk-2
[root@pcmk-1 ~]# stonith_admin --reboot pcmk-2

After a successful test, login to any rebooted nodes, and start the cluster (with pcs cluster start).

Chapter 9. Convert Cluster to Active/Active

Table of Contents

9.1. Install Cluster Filesystem Software
9.2. Configure the Cluster for the DLM
9.3. Create and Populate GFS2 Filesystem
9.4. Reconfigure the Cluster for GFS2
9.5. Clone the IP address
9.6. Clone the Filesystem and Apache Resources
9.7. Test Failover

The primary requirement for an Active/Active cluster is that the data required for your services is available, simultaneously, on both machines. Pacemaker makes no requirement on how this is achieved; you could use a SAN if you had one available, but since DRBD supports multiple Primaries, we can continue to use it here.

9.1. Install Cluster Filesystem Software

The only hitch is that we need to use a cluster-aware filesystem. The one we used earlier with DRBD, xfs, is not one of those. Both OCFS2 and GFS2 are supported; here, we will use GFS2.

On both nodes, install the GFS2 command-line utilities and the Distributed Lock Manager (DLM) required by cluster filesystems:

# yum install -y gfs2-utils dlm

9.2. Configure the Cluster for the DLM

The DLM needs to run on both nodes, so we’ll start by creating a resource for it (using the ocf:pacemaker:controld resource script), and clone it:

[root@pcmk-1 ~]# pcs cluster cib dlm_cfg
[root@pcmk-1 ~]# pcs -f dlm_cfg resource create dlm ocf:pacemaker:controld op monitor interval=60s
[root@pcmk-1 ~]# pcs -f dlm_cfg resource clone dlm clone-max=2 clone-node-max=1
[root@pcmk-1 ~]# pcs -f dlm_cfg resource show
 ClusterIP      (ocf::heartbeat:IPaddr2):       Started
 WebSite        (ocf::heartbeat:apache):        Started
 Master/Slave Set: WebDataClone [WebData]
     Masters: [ pcmk-2 ]
     Slaves: [ pcmk-1 ]
 WebFS  (ocf::heartbeat:Filesystem):    Started
 Clone Set: dlm-clone [dlm]
     Stopped: [ pcmk-1 pcmk-2 ]

Activate our new configuration, and see how the cluster responds:

[root@pcmk-1 ~]# pcs cluster cib-push dlm_cfg
CIB updated
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Fri Aug 14 11:19:36 2015
Last change: Fri Aug 14 11:19:28 2015
Stack: corosync
Current DC: pcmk-1 (1) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
8 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:

 ClusterIP      (ocf::heartbeat:IPaddr2):       Started pcmk-2
 WebSite        (ocf::heartbeat:apache):        Started pcmk-2
 Master/Slave Set: WebDataClone [WebData]
     Masters: [ pcmk-2 ]
     Slaves: [ pcmk-1 ]
 WebFS  (ocf::heartbeat:Filesystem):    Started pcmk-2
 ipmi-fencing   (stonith:fence_ipmilan):        Started pcmk-1
 Clone Set: dlm-clone [dlm]
     Started: [ pcmk-1 pcmk-2 ]

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

9.3. Create and Populate GFS2 Filesystem

Before we do anything to the existing partition, we need to make sure it is unmounted. We do this by telling the cluster to stop the WebFS resource. This will ensure that other resources (in our case, Apache) using WebFS are not only stopped, but stopped in the correct order.

[root@pcmk-1 ~]# pcs resource disable WebFS
[root@pcmk-1 ~]# pcs resource
 ClusterIP      (ocf::heartbeat:IPaddr2):       Started
 WebSite        (ocf::heartbeat:apache):        Stopped
 Master/Slave Set: WebDataClone [WebData]
     Masters: [ pcmk-2 ]
     Slaves: [ pcmk-1 ]
 WebFS  (ocf::heartbeat:Filesystem):    Stopped
 Clone Set: dlm-clone [dlm]
     Started: [ pcmk-1 pcmk-2 ]

You can see that both Apache and WebFS have been stopped, and that pcmk-2 is the current master for the DRBD device.

Now we can create a new GFS2 filesystem on the DRBD device.

Warning

This will erase all previous content stored on the DRBD device. Ensure you have a copy of any important data.

Important

Run the next command on whichever node has the DRBD Primary role. Otherwise, you will receive the message:

/dev/drbd1: Read-only file system

[root@pcmk-2 ~]# mkfs.gfs2 -p lock_dlm -j 2 -t mycluster:web /dev/drbd1
It appears to contain an existing filesystem (xfs)
This will destroy any data on /dev/drbd1
Are you sure you want to proceed? [y/n]y
Device:                    /dev/drbd1
Block size:                4096
Device size:               1.00 GB (262127 blocks)
Filesystem size:           1.00 GB (262126 blocks)
Journals:                  2
Resource groups:           5
Locking protocol:          "lock_dlm"
Lock table:                "mycluster:web"
UUID:                      9a72c488-d8a7-24c9-ceee-add7a8ca52c2

The mkfs.gfs2 command required a number of additional parameters:

-p lock_dlm specifies that we want to use the kernel’s DLM.
-j 2 indicates that the filesystem should reserve enough space for two journals (one for each node that will access the filesystem).
-t mycluster:web specifies the lock table name. The format for this field is clustername:fsname. For clustername, we need to use the same value we specified originally with pcs cluster setup --name (which is also the value of cluster_name in /etc/corosync/corosync.conf). If you are unsure what your cluster name is, you can look in /etc/corosync/corosync.conf or execute the command pcs cluster corosync pcmk-1 | grep cluster_name.

Now we can (re-)populate the new filesystem with data (web pages). We’ll create yet another variation on our home page.

[root@pcmk-2 ~]# mount /dev/drbd1 /mnt
[root@pcmk-2 ~]# cat <<-END >/mnt/index.html
<html>
<body>My Test Site - GFS2</body>
</html>
END
[root@pcmk-2 ~]# chcon -R --reference=/var/www/html /mnt
[root@pcmk-2 ~]# umount /dev/drbd1
[root@pcmk-2 ~]# drbdadm verify wwwdata

9.4. Reconfigure the Cluster for GFS2

With the WebFS resource stopped, let’s update the configuration.

[root@pcmk-1 ~]# pcs resource show WebFS
 Resource: WebFS (class=ocf provider=heartbeat type=Filesystem)
  Attributes: device=/dev/drbd1 directory=/var/www/html fstype=xfs
  Meta Attrs: target-role=Stopped
  Operations: start interval=0s timeout=60 (WebFS-start-timeout-60)
              stop interval=0s timeout=60 (WebFS-stop-timeout-60)
              monitor interval=20 timeout=40 (WebFS-monitor-interval-20)

The fstype option needs to be updated to gfs2 instead of xfs.

[root@pcmk-1 ~]# pcs resource update WebFS fstype=gfs2
[root@pcmk-1 ~]# pcs resource show WebFS
 Resource: WebFS (class=ocf provider=heartbeat type=Filesystem)
  Attributes: device=/dev/drbd1 directory=/var/www/html fstype=gfs2
  Meta Attrs: target-role=Stopped
  Operations: start interval=0s timeout=60 (WebFS-start-timeout-60)
              stop interval=0s timeout=60 (WebFS-stop-timeout-60)
              monitor interval=20 timeout=40 (WebFS-monitor-interval-20)

GFS2 requires that DLM be running, so we also need to set up new colocation and ordering constraints for it:

[root@pcmk-1 ~]# pcs constraint colocation add WebFS with dlm-clone INFINITY
[root@pcmk-1 ~]# pcs constraint order dlm-clone then WebFS
Adding dlm-clone WebFS (kind: Mandatory) (Options: first-action=start then-action=start)

9.5. Clone the IP address

There’s no point making the services active on both locations if we can’t reach them both, so let’s clone the IP address.

The IPaddr2 resource agent has built-in intelligence for when it is configured as a clone. It will utilize a multicast MAC address to have the local switch send the relevant packets to all nodes in the cluster, together with iptables clusterip rules on the nodes so that any given packet will be grabbed by exactly one node. This will give us a simple but effective form of load-balancing requests between our two nodes.

Let’s start a new config, and clone our IP:

[root@pcmk-1 ~]# pcs cluster cib loadbalance_cfg
[root@pcmk-1 ~]# pcs -f loadbalance_cfg resource clone ClusterIP \
     clone-max=2 clone-node-max=2 globally-unique=true

clone-max=2 tells the resource agent to split packets this many ways. This should equal the number of nodes that can host the IP.
clone-node-max=2 says that one node can run up to 2 instances of the clone. This should also equal the number of nodes that can host the IP, so that if any node goes down, another node can take over the failed node’s "request bucket". Otherwise, requests intended for the failed node would be discarded.
globally-unique=true tells the cluster that one clone isn’t identical to another (each handles a different "bucket"). This also tells the resource agent to insert iptables rules so each host only processes packets in its bucket(s).

Notice that when the ClusterIP becomes a clone, the constraints referencing ClusterIP now reference the clone. This is done automatically by pcs.

[root@pcmk-1 ~]# pcs -f loadbalance_cfg constraint
Location Constraints:
Ordering Constraints:
  start ClusterIP-clone then start WebSite (kind:Mandatory)
  promote WebDataClone then start WebFS (kind:Mandatory)
  start WebFS then start WebSite (kind:Mandatory)
  start dlm-clone then start WebFS (kind:Mandatory)
Colocation Constraints:
  WebSite with ClusterIP-clone (score:INFINITY)
  WebFS with WebDataClone (score:INFINITY) (with-rsc-role:Master)
  WebSite with WebFS (score:INFINITY)
  WebFS with dlm-clone (score:INFINITY)

Now we must tell the resource how to decide which requests are processed by which hosts. To do this, we specify the clusterip_hash parameter. The value of sourceip means that the source IP address of incoming packets will be hashed; each node will process a certain range of hashes.

[root@pcmk-1 ~]# pcs -f loadbalance_cfg resource update ClusterIP clusterip_hash=sourceip

Load our configuration to the cluster, and see how it responds.

[root@pcmk-1 ~]# pcs cluster cib-push loadbalance_cfg
CIB updated
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Fri Aug 14 11:32:07 2015
Last change: Fri Aug 14 11:32:04 2015
Stack: corosync
Current DC: pcmk-1 (1) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
9 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:

 WebSite        (ocf::heartbeat:apache):        Stopped
 Master/Slave Set: WebDataClone [WebData]
     Masters: [ pcmk-1 ]
     Slaves: [ pcmk-2 ]
 WebFS  (ocf::heartbeat:Filesystem):    Stopped
 ipmi-fencing   (stonith:fence_ipmilan):        Started pcmk-1
 Clone Set: dlm-clone [dlm]
     Started: [ pcmk-1 pcmk-2 ]
 Clone Set: ClusterIP-clone [ClusterIP] (unique)
     ClusterIP:0        (ocf::heartbeat:IPaddr2):       Started pcmk-1
     ClusterIP:1        (ocf::heartbeat:IPaddr2):       Started pcmk-2

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

If desired, you can demonstrate that all request buckets are working by using a tool such as arping from several source hosts to see which host responds to each.

9.6. Clone the Filesystem and Apache Resources

Now that we have a cluster filesystem ready to go, and our nodes can load-balance requests to a shared IP address, we can configure the cluster so both nodes mount the filesystem and respond to web requests.

Clone the filesystem and Apache resources in a new configuration. Notice how pcs automatically updates the relevant constraints again.

[root@pcmk-1 ~]# pcs cluster cib active_cfg
[root@pcmk-1 ~]# pcs -f active_cfg resource clone WebFS
[root@pcmk-1 ~]# pcs -f active_cfg resource clone WebSite
[root@pcmk-1 ~]# pcs -f active_cfg constraint
Location Constraints:
Ordering Constraints:
  start ClusterIP-clone then start WebSite-clone (kind:Mandatory)
  promote WebDataClone then start WebFS-clone (kind:Mandatory)
  start WebFS-clone then start WebSite-clone (kind:Mandatory)
  start dlm-clone then start WebFS-clone (kind:Mandatory)
Colocation Constraints:
  WebSite-clone with ClusterIP-clone (score:INFINITY)
  WebFS-clone with WebDataClone (score:INFINITY) (with-rsc-role:Master)
  WebSite-clone with WebFS-clone (score:INFINITY)
  WebFS-clone with dlm-clone (score:INFINITY)

Tell the cluster that it is now allowed to promote both instances to be DRBD Primary (aka. master).

[root@pcmk-1 ~]# pcs -f active_cfg resource update WebDataClone master-max=2

Finally, load our configuration to the cluster, and re-enable the WebFS resource (which we disabled earlier).

[root@pcmk-1 ~]# pcs cluster cib-push active_cfg
CIB updated
[root@pcmk-1 ~]# pcs resource enable WebFS

After all the processes are started, the status should look similar to this.

[root@pcmk-1 ~]# pcs resource
 Master/Slave Set: WebDataClone [WebData]
     Masters: [ pcmk-1 pcmk-2 ]
 Clone Set: dlm-clone [dlm]
     Started: [ pcmk-1 pcmk-2 ]
 Clone Set: ClusterIP-clone [ClusterIP] (unique)
     ClusterIP:0        (ocf::heartbeat:IPaddr2):       Started
     ClusterIP:1        (ocf::heartbeat:IPaddr2):       Started
 Clone Set: WebFS-clone [WebFS]
     Started: [ pcmk-1 pcmk-2 ]
 Clone Set: WebSite-clone [WebSite]
     Started: [ pcmk-1 pcmk-2 ]

9.7. Test Failover

Testing failover is left as an exercise for the reader. For example, you can put one node into standby mode, use pcs status to confirm that its ClusterIP clone was moved to the other node, and use arping to verify that packets are not being lost from any source host.

Note

You may find that when a failed node rejoins the cluster, both ClusterIP clones stay on one node, due to the resource stickiness. While this works fine, it effectively eliminates load-balancing and returns the cluster to an active-passive setup again. You can avoid this by disabling stickiness for the IP address resource:

[root@pcmk-1 ~]# pcs resource meta ClusterIP resource-stickiness=0

Configuration Recap

Table of Contents

A.1. Final Cluster Configuration

A.2. Node List

A.3. Cluster Options

A.4. Resources

A.4.1. Default Options
A.4.2. Fencing
A.4.3. Service Address
A.4.4. DRBD - Shared Storage
A.4.5. Cluster Filesystem
A.4.6. Apache

A.1. Final Cluster Configuration

[root@pcmk-1 ~]# pcs resource
 Master/Slave Set: WebDataClone [WebData]
     Masters: [ pcmk-1 pcmk-2 ]
 Clone Set: dlm-clone [dlm]
     Started: [ pcmk-1 pcmk-2 ]
 Clone Set: ClusterIP-clone [ClusterIP] (unique)
     ClusterIP:0        (ocf::heartbeat:IPaddr2):       Started
     ClusterIP:1        (ocf::heartbeat:IPaddr2):       Started
 Clone Set: WebFS-clone [WebFS]
     Started: [ pcmk-1 pcmk-2 ]
 Clone Set: WebSite-clone [WebSite]
     Started: [ pcmk-1 pcmk-2 ]

[root@pcmk-1 ~]# pcs resource op defaults
timeout: 240s

[root@pcmk-1 ~]# pcs stonith
 impi-fencing   (stonith:fence_ipmilan) Started

[root@pcmk-1 ~]# pcs constraint
Location Constraints:
Ordering Constraints:
  start ClusterIP-clone then start WebSite-clone (kind:Mandatory)
  promote WebDataClone then start WebFS-clone (kind:Mandatory)
  start WebFS-clone then start WebSite-clone (kind:Mandatory)
  start dlm-clone then start WebFS-clone (kind:Mandatory)
Colocation Constraints:
  WebSite-clone with ClusterIP-clone (score:INFINITY)
  WebFS-clone with WebDataClone (score:INFINITY) (with-rsc-role:Master)
  WebSite-clone with WebFS-clone (score:INFINITY)
  WebFS-clone with dlm-clone (score:INFINITY)

[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Fri Aug 14 12:05:37 2015
Last change: Fri Aug 14 11:49:29 2015
Stack: corosync
Current DC: pcmk-1 (1) - partition with quorum
Version: 1.1.12-a14efad
2 Nodes configured
11 Resources configured


Online: [ pcmk-1 pcmk-2 ]

Full list of resources:

 impi-fencing   (stonith:fence_ipmilan):        Started pcmk-1
 Master/Slave Set: WebDataClone [WebData]
     Masters: [ pcmk-1 pcmk-2 ]
 Clone Set: dlm-clone [dlm]
     Started: [ pcmk-1 pcmk-2 ]
 Clone Set: ClusterIP-clone [ClusterIP] (unique)
     ClusterIP:0        (ocf::heartbeat:IPaddr2):       Started pcmk-2
     ClusterIP:1        (ocf::heartbeat:IPaddr2):       Started pcmk-1
 Clone Set: WebFS-clone [WebFS]
     Started: [ pcmk-1 pcmk-2 ]
 Clone Set: WebSite-clone [WebSite]
     Started: [ pcmk-1 pcmk-2 ]

PCSD Status:
  pcmk-1: Online
  pcmk-2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled

[root@pcmk-1 ~]# pcs cluster cib

<cib crm_feature_set="3.0.9" validate-with="pacemaker-2.3" epoch="51" num_updates="16" admin_epoch="0" cib-last-written="Fri Aug 14 11:49:29 2015" have-quorum="1" dc-uuid="1">
    <crm_config>
      <cluster_property_set id="cib-bootstrap-options">
        <nvpair id="cib-bootstrap-options-have-watchdog" name="have-watchdog" value="false"/>
        <nvpair id="cib-bootstrap-options-dc-version" name="dc-version" value="1.1.12-a14efad"/>
        <nvpair id="cib-bootstrap-options-cluster-infrastructure" name="cluster-infrastructure" value="corosync"/>
        <nvpair id="cib-bootstrap-options-cluster-name" name="cluster-name" value="mycluster"/>
        <nvpair id="cib-bootstrap-options-last-lrm-refresh" name="last-lrm-refresh" value="1419129162"/>
        <nvpair id="cib-bootstrap-options-stonith-enabled" name="stonith-enabled" value="true"/>
      </cluster_property_set>
    </crm_config>
    <nodes>
      <node id="1" uname="pcmk-1">
        <instance_attributes id="nodes-1"/>
      </node>
      <node id="2" uname="pcmk-2">
        <instance_attributes id="nodes-2"/>
      </node>
    </nodes>
    <resources>
      <primitive class="stonith" id="impi-fencing" type="fence_ipmilan">
        <instance_attributes id="impi-fencing-instance_attributes">
          <nvpair id="impi-fencing-instance_attributes-pcmk_host_list" name="pcmk_host_list" value="pcmk-1 pcmk-2"/>
          <nvpair id="impi-fencing-instance_attributes-ipaddr" name="ipaddr" value="10.0.0.1"/>
          <nvpair id="impi-fencing-instance_attributes-login" name="login" value="testuser"/>
          <nvpair id="impi-fencing-instance_attributes-passwd" name="passwd" value="acd123"/>
        </instance_attributes>
        <operations>
          <op id="impi-fencing-interval-60s" interval="60s" name="monitor"/>
        </operations>
      </primitive>
      <master id="WebDataClone">
        <primitive class="ocf" id="WebData" provider="linbit" type="drbd">
          <instance_attributes id="WebData-instance_attributes">
            <nvpair id="WebData-instance_attributes-drbd_resource" name="drbd_resource" value="wwwdata"/>
          </instance_attributes>
          <operations>
            <op id="WebData-start-timeout-240" interval="0s" name="start" timeout="240"/>
            <op id="WebData-promote-timeout-90" interval="0s" name="promote" timeout="90"/>
            <op id="WebData-demote-timeout-90" interval="0s" name="demote" timeout="90"/>
            <op id="WebData-stop-timeout-100" interval="0s" name="stop" timeout="100"/>
            <op id="WebData-monitor-interval-60s" interval="60s" name="monitor"/>
          </operations>
        </primitive>
        <meta_attributes id="WebDataClone-meta_attributes">
          <nvpair id="WebDataClone-meta_attributes-master-max" name="master-max" value="2"/>
          <nvpair id="WebDataClone-meta_attributes-master-node-max" name="master-node-max" value="1"/>
          <nvpair id="WebDataClone-meta_attributes-clone-max" name="clone-max" value="2"/>
          <nvpair id="WebDataClone-meta_attributes-clone-node-max" name="clone-node-max" value="1"/>
          <nvpair id="WebDataClone-meta_attributes-notify" name="notify" value="true"/>
        </meta_attributes>
      </master>
      <clone id="dlm-clone">
        <primitive class="ocf" id="dlm" provider="pacemaker" type="controld">
          <instance_attributes id="dlm-instance_attributes"/>
          <operations>
            <op id="dlm-start-timeout-90" interval="0s" name="start" timeout="90"/>
            <op id="dlm-stop-timeout-100" interval="0s" name="stop" timeout="100"/>
            <op id="dlm-monitor-interval-60s" interval="60s" name="monitor"/>
          </operations>
        </primitive>
        <meta_attributes id="dlm-clone-meta">
          <nvpair id="dlm-clone-max" name="clone-max" value="2"/>
          <nvpair id="dlm-clone-node-max" name="clone-node-max" value="1"/>
        </meta_attributes>
      </clone>
      <clone id="ClusterIP-clone">
        <primitive class="ocf" id="ClusterIP" provider="heartbeat" type="IPaddr2">
          <instance_attributes id="ClusterIP-instance_attributes">
            <nvpair id="ClusterIP-instance_attributes-ip" name="ip" value="192.168.122.120"/>
            <nvpair id="ClusterIP-instance_attributes-cidr_netmask" name="cidr_netmask" value="32"/>
            <nvpair id="ClusterIP-instance_attributes-clusterip_hash" name="clusterip_hash" value="sourceip"/>
          </instance_attributes>
          <operations>
            <op id="ClusterIP-start-timeout-20s" interval="0s" name="start" timeout="20s"/>
            <op id="ClusterIP-stop-timeout-20s" interval="0s" name="stop" timeout="20s"/>
            <op id="ClusterIP-monitor-interval-30s" interval="30s" name="monitor"/>
          </operations>
          <meta_attributes id="ClusterIP-meta_attributes"/>
        </primitive>
        <meta_attributes id="ClusterIP-clone-meta">
          <nvpair id="ClusterIP-clone-max" name="clone-max" value="2"/>
          <nvpair id="ClusterIP-clone-node-max" name="clone-node-max" value="2"/>
          <nvpair id="ClusterIP-globally-unique" name="globally-unique" value="true"/>
        </meta_attributes>
      </clone>
      <clone id="WebFS-clone">
        <primitive class="ocf" id="WebFS" provider="heartbeat" type="Filesystem">
          <instance_attributes id="WebFS-instance_attributes">
            <nvpair id="WebFS-instance_attributes-device" name="device" value="/dev/drbd1"/>
            <nvpair id="WebFS-instance_attributes-directory" name="directory" value="/var/www/html"/>
            <nvpair id="WebFS-instance_attributes-fstype" name="fstype" value="gfs2"/>
          </instance_attributes>
          <operations>
            <op id="WebFS-start-timeout-60" interval="0s" name="start" timeout="60"/>
            <op id="WebFS-stop-timeout-60" interval="0s" name="stop" timeout="60"/>
            <op id="WebFS-monitor-interval-20" interval="20" name="monitor" timeout="40"/>
          </operations>
          <meta_attributes id="WebFS-meta_attributes"/>
        </primitive>
        <meta_attributes id="WebFS-clone-meta"/>
      </clone>
      <clone id="WebSite-clone">
        <primitive class="ocf" id="WebSite" provider="heartbeat" type="apache">
          <instance_attributes id="WebSite-instance_attributes">
            <nvpair id="WebSite-instance_attributes-configfile" name="configfile" value="/etc/httpd/conf/httpd.conf"/>
            <nvpair id="WebSite-instance_attributes-statusurl" name="statusurl" value="http://localhost/server-status"/>
          </instance_attributes>
          <operations>
            <op id="WebSite-start-timeout-40s" interval="0s" name="start" timeout="40s"/>
            <op id="WebSite-stop-timeout-60s" interval="0s" name="stop" timeout="60s"/>
            <op id="WebSite-monitor-interval-1min" interval="1min" name="monitor"/>
          </operations>
        </primitive>
        <meta_attributes id="WebSite-clone-meta"/>
      </clone>
    </resources>
    <constraints>
      <rsc_colocation id="colocation-WebSite-ClusterIP-INFINITY" rsc="WebSite-clone" score="INFINITY" with-rsc="ClusterIP-clone"/>
      <rsc_order first="ClusterIP-clone" first-action="start" id="order-ClusterIP-WebSite-mandatory" then="WebSite-clone" then-action="start"/>
      <rsc_colocation id="colocation-WebFS-WebDataClone-INFINITY" rsc="WebFS-clone" score="INFINITY" with-rsc="WebDataClone" with-rsc-role="Master"/>
      <rsc_order first="WebDataClone" first-action="promote" id="order-WebDataClone-WebFS-mandatory" then="WebFS-clone" then-action="start"/>
      <rsc_colocation id="colocation-WebSite-WebFS-INFINITY" rsc="WebSite-clone" score="INFINITY" with-rsc="WebFS-clone"/>
      <rsc_order first="WebFS-clone" first-action="start" id="order-WebFS-WebSite-mandatory" then="WebSite-clone" then-action="start"/>
      <rsc_colocation id="colocation-WebFS-clone-dlm-clone-INFINITY" rsc="WebFS-clone" score="INFINITY" with-rsc="dlm-clone"/>
      <rsc_order first="dlm-clone" first-action="start" id="order-dlm-clone-WebFS-clone-mandatory" then="WebFS-clone" then-action="start"/>
    </constraints>
    <rsc_defaults>
      <meta_attributes id="rsc_defaults-options">
        <nvpair id="rsc_defaults-options-resource-stickiness" name="resource-stickiness" value="100"/>
      </meta_attributes>
    </rsc_defaults>
    <op_defaults>
      <meta_attributes id="op_defaults-options">
        <nvpair id="op_defaults-options-timeout" name="timeout" value="240s"/>
      </meta_attributes>
    </op_defaults>
  </configuration>
  <status>
    <node_state id="1" uname="pcmk-1" in_ccm="true" crmd="online" crm-debug-origin="do_update_resource" join="member" expected="member">
      <lrm id="1">
        <lrm_resources>
          <lrm_resource id="WebData" type="drbd" class="ocf" provider="linbit">
            <lrm_rsc_op id="WebData_last_0" operation_key="WebData_promote_0" operation="promote" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="13:4:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;13:4:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="44" rc-code="0" op-status="0" interval="0" last-run="1419264508" last-rc-change="1419264508" exec-time="26" queue-time="0" op-digest="bc5c2e08730036ec602d79a958821da4" on_node="pcmk-1"/>
          </lrm_resource>
          <lrm_resource id="dlm" type="controld" class="ocf" provider="pacemaker">
            <lrm_rsc_op id="dlm_last_0" operation_key="dlm_start_0" operation="start" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="37:2:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;37:2:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="37" rc-code="0" op-status="0" interval="0" last-run="1419264506" last-rc-change="1419264506" exec-time="1041" queue-time="0" op-digest="f2317cad3d54cec5d7d7aa7d0bf35cf8" on_node="pcmk-1"/>
            <lrm_rsc_op id="dlm_monitor_60000" operation_key="dlm_monitor_60000" operation="monitor" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="39:3:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;39:3:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="38" rc-code="0" op-status="0" interval="60000" last-rc-change="1419264507" exec-time="11" queue-time="0" op-digest="968cc450c09e98fdac3043cb6a194d3d" on_node="pcmk-1"/>
          </lrm_resource>
          <lrm_resource id="ClusterIP:0" type="IPaddr2" class="ocf" provider="heartbeat">
            <lrm_rsc_op id="ClusterIP:0_last_0" operation_key="ClusterIP:0_monitor_0" operation="monitor" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="7:0:7:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:7;7:0:7:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="19" rc-code="7" op-status="0" interval="0" last-run="1419264506" last-rc-change="1419264506" exec-time="28" queue-time="0" op-digest="ac61ecc765070218997f6d876fa1d76c" on_node="pcmk-1"/>
          </lrm_resource>
          <lrm_resource id="ClusterIP:1" type="IPaddr2" class="ocf" provider="heartbeat">
            <lrm_rsc_op id="ClusterIP:1_last_0" operation_key="ClusterIP:1_start_0" operation="start" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="49:3:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;49:3:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="40" rc-code="0" op-status="0" interval="0" last-run="1419264507" last-rc-change="1419264507" exec-time="190" queue-time="0" op-digest="ac61ecc765070218997f6d876fa1d76c" on_node="pcmk-1"/>
            <lrm_rsc_op id="ClusterIP:1_monitor_30000" operation_key="ClusterIP:1_monitor_30000" operation="monitor" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="50:3:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;50:3:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="41" rc-code="0" op-status="0" interval="30000" last-rc-change="1419264507" exec-time="27" queue-time="0" op-digest="8ce33853c31576b708595f1d8a4a215c" on_node="pcmk-1"/>
          </lrm_resource>
          <lrm_resource id="WebFS" type="Filesystem" class="ocf" provider="heartbeat">
            <lrm_rsc_op id="WebFS_last_0" operation_key="WebFS_start_0" operation="start" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="62:5:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;62:5:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="46" rc-code="0" op-status="0" interval="0" last-run="1419264508" last-rc-change="1419264508" exec-time="585" queue-time="0" op-digest="9d797b0e3b7f9729195992c0dafb5a9e" on_node="pcmk-1"/>
            <lrm_rsc_op id="WebFS_monitor_20000" operation_key="WebFS_monitor_20000" operation="monitor" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="62:6:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;62:6:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="47" rc-code="0" op-status="0" interval="20000" last-rc-change="1419264508" exec-time="21" queue-time="1" op-digest="099af723b175851f09e5391e0c13854e" on_node="pcmk-1"/>
          </lrm_resource>
          <lrm_resource id="WebSite" type="apache" class="ocf" provider="heartbeat">
            <lrm_rsc_op id="WebSite_last_0" operation_key="WebSite_start_0" operation="start" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="72:6:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;72:6:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="48" rc-code="0" op-status="0" interval="0" last-run="1419264508" last-rc-change="1419264508" exec-time="65" queue-time="0" op-digest="49ba395a3f2c142631c2ef2c431a29d9" on_node="pcmk-1"/>
            <lrm_rsc_op id="WebSite_monitor_60000" operation_key="WebSite_monitor_60000" operation="monitor" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="73:6:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;73:6:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="49" rc-code="0" op-status="0" interval="60000" last-rc-change="1419264508" exec-time="26" queue-time="0" op-digest="eddc33bef3f1592ad847638ee485316f" on_node="pcmk-1"/>
          </lrm_resource>
        </lrm_resources>
      </lrm>
      <transient_attributes id="1">
        <instance_attributes id="status-1">
          <nvpair id="status-1-shutdown" name="shutdown" value="0"/>
          <nvpair id="status-1-probe_complete" name="probe_complete" value="true"/>
          <nvpair id="status-1-master-WebData" name="master-WebData" value="10000"/>
        </instance_attributes>
      </transient_attributes>
    </node_state>
    <node_state id="2" uname="pcmk-2" in_ccm="true" crmd="online" crm-debug-origin="do_update_resource" join="member" expected="member">
      <transient_attributes id="2">
        <instance_attributes id="status-2">
          <nvpair id="status-2-shutdown" name="shutdown" value="0"/>
          <nvpair id="status-2-probe_complete" name="probe_complete" value="true"/>
          <nvpair id="status-2-master-WebData" name="master-WebData" value="10000"/>
        </instance_attributes>
      </transient_attributes>
      <lrm id="2">
        <lrm_resources>
          <lrm_resource id="WebData" type="drbd" class="ocf" provider="linbit">
            <lrm_rsc_op id="WebData_last_0" operation_key="WebData_promote_0" operation="promote" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="16:4:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;16:4:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="41" rc-code="0" op-status="0" interval="0" last-run="1419264508" last-rc-change="1419264508" exec-time="26" queue-time="0" op-digest="bc5c2e08730036ec602d79a958821da4" on_node="pcmk-2"/>
          </lrm_resource>
          <lrm_resource id="dlm" type="controld" class="ocf" provider="pacemaker">
            <lrm_rsc_op id="dlm_last_0" operation_key="dlm_start_0" operation="start" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="35:2:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;35:2:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="34" rc-code="0" op-status="0" interval="0" last-run="1419264506" last-rc-change="1419264506" exec-time="1053" queue-time="0" op-digest="f2317cad3d54cec5d7d7aa7d0bf35cf8" on_node="pcmk-2"/>
            <lrm_rsc_op id="dlm_monitor_60000" operation_key="dlm_monitor_60000" operation="monitor" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="42:3:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;42:3:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="35" rc-code="0" op-status="0" interval="60000" last-rc-change="1419264507" exec-time="19" queue-time="0" op-digest="968cc450c09e98fdac3043cb6a194d3d" on_node="pcmk-2"/>
          </lrm_resource>
          <lrm_resource id="ClusterIP:0" type="IPaddr2" class="ocf" provider="heartbeat">
            <lrm_rsc_op id="ClusterIP:0_last_0" operation_key="ClusterIP:0_start_0" operation="start" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="47:3:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;47:3:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="36" rc-code="0" op-status="0" interval="0" last-run="1419264507" last-rc-change="1419264507" exec-time="237" queue-time="0" op-digest="ac61ecc765070218997f6d876fa1d76c" on_node="pcmk-2"/>
            <lrm_rsc_op id="ClusterIP:0_monitor_30000" operation_key="ClusterIP:0_monitor_30000" operation="monitor" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="51:4:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;51:4:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="39" rc-code="0" op-status="0" interval="30000" last-rc-change="1419264507" exec-time="34" queue-time="0" op-digest="8ce33853c31576b708595f1d8a4a215c" on_node="pcmk-2"/>
          </lrm_resource>
          <lrm_resource id="ClusterIP:1" type="IPaddr2" class="ocf" provider="heartbeat">
            <lrm_rsc_op id="ClusterIP:1_last_0" operation_key="ClusterIP:1_monitor_0" operation="monitor" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="16:0:7:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:7;16:0:7:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="23" rc-code="7" op-status="0" interval="0" last-run="1419264506" last-rc-change="1419264506" exec-time="28" queue-time="0" op-digest="ac61ecc765070218997f6d876fa1d76c" on_node="pcmk-2"/>
          </lrm_resource>
          <lrm_resource id="WebFS" type="Filesystem" class="ocf" provider="heartbeat">
            <lrm_rsc_op id="WebFS_last_0" operation_key="WebFS_start_0" operation="start" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="60:5:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;60:5:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="43" rc-code="0" op-status="0" interval="0" last-run="1419264508" last-rc-change="1419264508" exec-time="662" queue-time="0" op-digest="9d797b0e3b7f9729195992c0dafb5a9e" on_node="pcmk-2"/>
            <lrm_rsc_op id="WebFS_monitor_20000" operation_key="WebFS_monitor_20000" operation="monitor" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="65:6:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;65:6:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="44" rc-code="0" op-status="0" interval="20000" last-rc-change="1419264508" exec-time="29" queue-time="0" op-digest="099af723b175851f09e5391e0c13854e" on_node="pcmk-2"/>
          </lrm_resource>
          <lrm_resource id="WebSite" type="apache" class="ocf" provider="heartbeat">
            <lrm_rsc_op id="WebSite_last_0" operation_key="WebSite_start_0" operation="start" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="70:6:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;70:6:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="45" rc-code="0" op-status="0" interval="0" last-run="1419264508" last-rc-change="1419264508" exec-time="64" queue-time="0" op-digest="49ba395a3f2c142631c2ef2c431a29d9" on_node="pcmk-2"/>
            <lrm_rsc_op id="WebSite_monitor_60000" operation_key="WebSite_monitor_60000" operation="monitor" crm-debug-origin="do_update_resource" crm_feature_set="3.0.9" transition-key="71:6:0:225c8bc5-8fb0-49b6-9f75-337085b080de" transition-magic="0:0;71:6:0:225c8bc5-8fb0-49b6-9f75-337085b080de" call-id="46" rc-code="0" op-status="0" interval="60000" last-rc-change="1419264508" exec-time="28" queue-time="0" op-digest="eddc33bef3f1592ad847638ee485316f" on_node="pcmk-2"/>
          </lrm_resource>
        </lrm_resources>
      </lrm>
    </node_state>
  </status>
</cib>

A.2. Node List

[root@pcmk-1 ~]# pcs status nodes
Pacemaker Nodes:
 Online: pcmk-1 pcmk-2
 Standby:
 Offline:

A.3. Cluster Options

[root@pcmk-1 ~]# pcs property
Cluster Properties:
 cluster-infrastructure: corosync
 cluster-name: mycluster
 dc-version: 1.1.12-a14efad
 have-watchdog: false
 last-lrm-refresh: 1439569053
 stonith-enabled: true

The output shows state information automatically obtained about the cluster, including:

cluster-infrastructure - the cluster communications layer in use (heartbeat or corosync)
cluster-name - the cluster name chosen by the administrator when the cluster was created
dc-version - the version (including upstream source-code hash) of Pacemaker used on the Designated Controller

The output also shows options set by the administrator that control the way the cluster operates, including:

stonith-enabled=true - whether the cluster is allowed to use STONITH resources

A.4. Resources

A.4.1. Default Options

[root@pcmk-1 ~]# pcs resource defaults
resource-stickiness: 100

This shows cluster option defaults that apply to every resource that does not explicitly set the option itself. Above:

resource-stickiness - Specify the aversion to moving healthy resources to other machines

A.4.2. Fencing

[root@pcmk-1 ~]# pcs stonith show
 ipmi-fencing   (stonith:fence_ipmilan) Started
[root@pcmk-1 ~]# pcs stonith show ipmi-fencing
 Resource: ipmi-fencing (class=stonith type=fence_ipmilan)
  Attributes: ipaddr="10.0.0.1" login="testuser" passwd="acd123" pcmk_host_list="pcmk-1 pcmk-2"
  Operations: monitor interval=60s (fence-monitor-interval-60s)

A.4.3. Service Address

Users of the services provided by the cluster require an unchanging address with which to access it. Additionally, we cloned the address so it will be active on both nodes. An iptables rule (created as part of the resource agent) is used to ensure that each request only gets processed by one of the two clone instances. The additional meta options tell the cluster that we want two instances of the clone (one "request bucket" for each node) and that if one node fails, then the remaining node should hold both.

[root@pcmk-1 ~]# pcs resource show ClusterIP-clone
 Clone: ClusterIP-clone
  Meta Attrs: clone-max=2 clone-node-max=2 globally-unique=true
  Resource: ClusterIP (class=ocf provider=heartbeat type=IPaddr2)
   Attributes: ip=192.168.122.120 cidr_netmask=32 clusterip_hash=sourceip
   Operations: start interval=0s timeout=20s (ClusterIP-start-timeout-20s)
               stop interval=0s timeout=20s (ClusterIP-stop-timeout-20s)
               monitor interval=30s (ClusterIP-monitor-interval-30s)

A.4.4. DRBD - Shared Storage

Here, we define the DRBD service and specify which DRBD resource (from /etc/drbd.d/*.res) it should manage. We make it a master/slave resource and, in order to have an active/active setup, allow both instances to be promoted to master at the same time. We also set the notify option so that the cluster will tell DRBD agent when its peer changes state.

[root@pcmk-1 ~]# pcs resource show WebDataClone
 Master: WebDataClone
  Meta Attrs: master-max=2 master-node-max=1 clone-max=2 clone-node-max=1 notify=true
  Resource: WebData (class=ocf provider=linbit type=drbd)
   Attributes: drbd_resource=wwwdata
   Operations: start interval=0s timeout=240 (WebData-start-timeout-240)
               promote interval=0s timeout=90 (WebData-promote-timeout-90)
               demote interval=0s timeout=90 (WebData-demote-timeout-90)
               stop interval=0s timeout=100 (WebData-stop-timeout-100)
               monitor interval=60s (WebData-monitor-interval-60s)
[root@pcmk-1 ~]# pcs constraint ref WebDataClone
Resource: WebDataClone
  colocation-WebFS-WebDataClone-INFINITY
  order-WebDataClone-WebFS-mandatory

A.4.5. Cluster Filesystem

The cluster filesystem ensures that files are read and written correctly. We need to specify the block device (provided by DRBD), where we want it mounted and that we are using GFS2. Again, it is a clone because it is intended to be active on both nodes. The additional constraints ensure that it can only be started on nodes with active DLM and DRBD instances.

[root@pcmk-1 ~]# pcs resource show WebFS-clone
 Clone: WebFS-clone
  Resource: WebFS (class=ocf provider=heartbeat type=Filesystem)
   Attributes: device=/dev/drbd1 directory=/var/www/html fstype=gfs2
   Operations: start interval=0s timeout=60 (WebFS-start-timeout-60)
               stop interval=0s timeout=60 (WebFS-stop-timeout-60)
               monitor interval=20 timeout=40 (WebFS-monitor-interval-20)
[root@pcmk-1 ~]# pcs constraint ref WebFS-clone
Resource: WebFS-clone
  colocation-WebFS-WebDataClone-INFINITY
  colocation-WebSite-WebFS-INFINITY
  colocation-WebFS-clone-dlm-clone-INFINITY
  order-WebDataClone-WebFS-mandatory
  order-WebFS-WebSite-mandatory
  order-dlm-clone-WebFS-clone-mandatory

A.4.6. Apache

Lastly, we have the actual service, Apache. We need only tell the cluster where to find its main configuration file and restrict it to running on nodes that have the required filesystem mounted and the IP address active.

[root@pcmk-1 ~]# pcs resource show WebSite-clone
 Clone: WebSite-clone
  Resource: WebSite (class=ocf provider=heartbeat type=apache)
   Attributes: configfile=/etc/httpd/conf/httpd.conf statusurl=http://localhost/server-status
   Operations: start interval=0s timeout=40s (WebSite-start-timeout-40s)
               stop interval=0s timeout=60s (WebSite-stop-timeout-60s)
               monitor interval=1min (WebSite-monitor-interval-1min)
[root@pcmk-1 ~]# pcs constraint ref WebSite-clone
Resource: WebSite-clone
  colocation-WebSite-ClusterIP-INFINITY
  colocation-WebSite-WebFS-INFINITY
  order-ClusterIP-WebSite-mandatory
  order-WebFS-WebSite-mandatory

Sample Corosync Configuration

Sample corosync.conf for two-node cluster created by pcs.

totem {
version: 2
secauth: off
cluster_name: mycluster
transport: udpu
}

nodelist {
  node {
        ring0_addr: pcmk-1
        nodeid: 1
       }
  node {
        ring0_addr: pcmk-2
        nodeid: 2
       }
}

quorum {
provider: corosync_votequorum
two_node: 1
}

logging {
to_syslog: yes
}

Revision History

Revision History

Revision 1-0

Mon May 17 2010

Andrew Beekhof

Import from Pages.app

Revision 2-0

Wed Sep 22 2010

Raoul Scarazzini

Italian translation

Revision 3-0

Wed Feb 9 2011

Andrew Beekhof

Updated for Fedora 13

Revision 4-0

Wed Oct 5 2011

Andrew Beekhof

Update the GFS2 section to use CMAN

Revision 5-0

Fri Feb 10 2012

Andrew Beekhof

Generate docbook content from asciidoc sources

Revision 6-0

Tues July 3 2012

Andrew Beekhof

Updated for Fedora 17

Revision 7-0

Fri Sept 14 2012

David Vossel

Updated for pcs

Revision 8-0

Mon Jan 05 2015

Ken Gaillot

Updated for Fedora 21

Revision 8-1

Thu Jan 08 2015

Ken Gaillot

Minor corrections, plus use include file for intro

Revision 9-0

Fri Aug 14 2015

Ken Gaillot

Update for CentOS 7.1 and leaving firewalld/SELinux enabled

Index

C

Creating and Activating a new SSH Key, Configure SSH

D

Domain name (Query), Use Short Node Names
Domain name (Remove from host name), Use Short Node Names

F

feedback

contact information for this manual, We Need Feedback!

N

Nodes

Domain name (Query), Use Short Node Names
Domain name (Remove from host name), Use Short Node Names
short name, Use Short Node Names

S

short name, Use Short Node Names
SSH, Configure SSH

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PREV 이전 1 NEXT 다음

IBM PowerLinux/PaceMaker - Cluster

■ 소개

■ 점수 값의 큰 노드에서 자원 시작

■ location에서 시작 노드를 제약

■ colocation에서 동거하는 자원을 제약

■ order 순서를 제약

■ 실험 1 colocation 점수 값을 -INFINITY에 보면

■ 실험 2 order 점수 값을 INFINITY에 보면

■ 실험 3 속성 값을 평가하는

■ お わ り に

'IBM PowerLinux > PaceMaker - Cluster' 카테고리의 다른 글

Pacemaker의 기능과 대응 가능한 고장

일반적인 클러스터 구성

데이터 인계 방법에 따른 분류

노드 대수에 따른 분류

Pacemaker와 가동률

Pacemaker 버전의 선택

자원 및 자원 에이전트

좌우 분열과 배타 제어

'IBM PowerLinux > PaceMaker - Cluster' 카테고리의 다른 글

'IBM PowerLinux > PaceMaker - Cluster' 카테고리의 다른 글

소개

HA 클러스터는?

Pacemaker의 기본 기능은?

클러스터 제어 기능

리소스 제어 기능

Pacemaker라고 어떻게 태어나요?

Linux-HA Japan 프로젝트는?

칼럼 : Pacemaker 로고 이모저모 [그 1]

'IBM PowerLinux > PaceMaker - Cluster' 카테고리의 다른 글

'IBM PowerLinux > PaceMaker - Cluster' 카테고리의 다른 글

'IBM PowerLinux > PaceMaker - Cluster' 카테고리의 다른 글

Clusters from Scratch

Step-by-Step Instructions for Building Your First High-Availability Cluster

Andrew Beekhof

Raoul Scarazzini

Dan Frîncu

Legal Notice

Preface

1. Document Conventions

1.1. Typographic Conventions

1.2. Pull-quote Conventions

1.3. Notes and Warnings

2. We Need Feedback!

Chapter 1. Read-Me-First

1.1. The Scope of this Document

1.2. What Is Pacemaker?

1.3. Pacemaker Architecture

1.3.1. Internal Components

1.4. Types of Pacemaker Clusters

Chapter 2. Installation

2.1. Install CentOS 7.1

2.1.1. Boot the Install Image

2.1.2. Installation Options

2.1.3. Configure Network

2.1.4. Configure Disk

2.1.5. Configure Time Synchronization

2.1.6. Finish Install

2.2. Configure the OS

2.2.1. Verify Networking

2.2.2. Login Remotely

2.2.3. Apply Updates

2.2.4. Use Short Node Names

2.3. Repeat for Second Node

2.4. Configure Communication Between Nodes

2.4.1. Configure Host Name Resolution

2.4.2. Configure SSH

2.5. Install the Cluster Software

2.6. Configure the Cluster Software

2.6.1. Allow cluster services through firewall

2.6.2. Enable pcs Daemon

2.6.3. Configure Corosync

Chapter 3. Pacemaker Tools

3.1. Simplify administration using a cluster shell

3.2. Explore pcs

Chapter 4. Start and Verify Cluster

4.1. Start the Cluster

4.2. Verify Corosync Installation

4.3. Verify Pacemaker Installation

Chapter 5. Create an Active/Passive Cluster

■ おわりに