[Pacemaker] stonith and avoiding split brain in two nodes cluster

Angel L. Mateo amateo at um.es
Mon Mar 25 15:01:28 EDT 2013

Jacek Konieczny <jajcus at jajcus.net> escribió:

>On Mon, 25 Mar 2013 13:54:22 +0100
>> 	My problem is how to avoid split brain situation with this 
>> configuration, without configuring a 3rd node. I have read about
>> quorum disks, external/sbd stonith plugin and other references, but
>> I'm too confused with all this.
>> 	For example, [1] mention techniques to improve quorum with
>> scsi reserve or quorum daemon, but it didn't point to how to do this
>> pacemaker. Or [2] talks about external/sbd.
>> 	Any help?
>With corosync 2.2 (2.1 too, I guess) you can use, in corosync.conf:
>quorum {
>	provider: corosync_votequorum
>	expected_votes: 2
>	two_node: 1
>Corosync will then manage quorum for the two-node cluster and Pacemaker

  I'm using corosync 1.1 which is the one  provided with my distribution (ubuntu 12.04). I could also use cman.

>can use that. You still need proper fencing to enforce the quorum (both
>for pacemaker and the storage layer – dlm in case you use clvmd), but
>extra quorum node is needed.
  I hace configured a dlm resource usted with clvm.

  One doubt... With this configuration, how split brain problem is handled?

>There is one more thing, though: you need two nodes active to boot the
>cluster, but then when one fails (and is fenced) the other may
>keeping quorum.
>	Jacek

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