[Pacemaker] DC election with downed node in 2-way cluster

[Miki Shapiro]

Hi all

I'm attempting to build a 2-way cluster, SLES-11-based with an openais/pacemaker stack. I've got the nodes and a resource (a drbd volume) happening. What I'm not sure about is the active CRM DC election process.

I configured a null stonith resource for each node.
I have stonith-enabled set to true ( I will implement a real stonith facility once final solution is in place)
I have no-quorum-policy set to ignore (as the cluster is expected to work with one node active).

I look at crm_mon or crm_gui, and it's all green and happy.

I now go and halt a node.

Observing crm_mon or crm_gui on node2, I expect to see :

1.       Services appear as down thanks to resource monitoring directives.

2.       The quorum broken (... do I care?)

3.       The new node elected as DC. Despite what the book states (here: < http://www.clusterlabs.org/doc/en-US/Pacemaker/1.0/html/Pacemaker_Explained/s-cluster-status.html > at the bottom)  that:

"The DC (Designated Controller) node is where all the decisions are made and if the current DC fails a new one is elected from the remaining cluster nodes. The choice of DC is of no significance to an administrator beyond the fact that its logs will generally be more interesting."



Is of significance. I want the brain, in as far as the surviving node is concerned, to be running on a non-halted server.


What happens in practice is:
If I halt the DC,

1.       Resources DO appear stopped and do-their-thing(tm)

2.       [PROBLEM?] Quorum DOES NOT appear as broken

3.       [PROBLEM?] The remaining node DOES NOT get (visibly) elected as the new DC.
If I halted the non-DC node,

1.       Resources DO appear stopped and do-their-thing(tm)

2.       Quorum DOES appear as broken

3.       [PROBLEM?]The remaining node DOES NOT get (visibly) elected as the new DC.

Now if my understanding serves me right, the DC is the baton-holding CRM that does the thinking for the entire cluster. If the surviving node1 think that the (DEAD) node2 is the de-facto brains of the cluster and doesn't take the reigns, I have a dysfunctional cluster.

Can someone please offer some clarification on how one would reasonably expect this to work?

Thanks!


Miki Shapiro
Linux Systems Engineer
Infrastructure Services & Operations

[cid:image001.png at 01CA9453.D1ECBD70]
745 Springvale Road
Mulgrave 3170 Australia
Email miki.shapiro at coles.com.au<mailto:miki.shapiro at coles.com.au>
Phone: 61 3 854 10520
Fax:     61 3 854 10558



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