Re: Two node Pacemaker with one Corosync only quorum node

Andrew Beekhof <[email protected]> Tue, 7 Oct 2014 14:10:02 +1100
Newsgroups	gmane.linux.highavailability.user
Message-ID	<[email protected]>
On 3 Sep 2014, at 9:29 am, Brian Campbell <[email protected]> wrote:

> I'm wondering if there are any problems that would occur if you ran a
> cluster with only two nodes running Pacemaker, but add a third Corosync
> only node to provide quorum.
> 
> I tried this setup, and it appears to work fine after some brief testing; I
> configured Corosync and votequorum appropriately on all three nodes, but
> only ever started Pacemaker on two of them. After enabling
> no-quorum-policy=stop, if I disconnected one of the nodes it would stop
> itself and the other would take over like I expect, rather than both nodes
> trying to promote themselves as occurs when there are only two nodes and
> no-quorum-policy=ignore (for the purposes of debugging and development, I
> don't have stonith enabled in order to make it easier to monitor what's
> going on at each node, without my connection dropping due to rebooting the
> machine).
> 
> I'm now wondering if there will be any problems I haven't anticipated with
> this setup, or anything I should look out for.

Its supposed to work and I've not heard anyone complain lately that it doesn't (possibly because no-one tried recently).
If you encounter any problems, definitely let us know.

> 
> Of course, other options would involve having the third node simply running
> Pacemaker but permanently in standby, or making it an asymmetric cluster
> and only allowing any resources to run on the first two nodes. But I'm
> curious if it's possible to go the simplest possible route and just have
> corosync running on a third quorum node; or possibly even more.
> 
> Our setup has a couple of master nodes with large amounts of RAM so that
> all of the metadata can fit into RAM, and then a number of cheap storage
> nodes to store the actual bulk data. Because we have the cheap storage
> nodes, we have a number of machines we can run as quorum-only nodes, but
> don't want to ever accidentally select them as a master or slave node.
> 
> Thanks,
> Brian
> 
> (as an aside, I'm wondering if this is the right list for this question, or
> if I should be asking it on the Pacemaker list instead; I haven't quite
> figured out where questions about interactions between Pacemaker and
> Corosync should be asked)
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> See also: http://linux-ha.org/ReportingProblems

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