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

Jacek Konieczny jajcus at jajcus.net
Mon Mar 25 10:54:10 EDT 2013

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
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 no
extra quorum node is needed.

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 continue,
keeping quorum.


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