[Pacemaker] Configuring a cluster for asymmetric operation

[Matthew O'Connor]

I ran across the same issue when putting together an asymmetric
cluster.  Generally, I've found that it's necessary to make sure all
nodes have the same resource-related backing software installed.  For
instance, I too have had to install DRBD on all nodes, even those not
running DRBD.  iSCSITarget is another one - even with the RA available,
not having the proper service available for the monitor to query can
cause a monitor error - which tends to nuke the resource on all nodes,
even the properly configured ones.  As it was explained to me, Pacemaker
needs to be able to know that a resource isn't (or is) running on a node
that it isn't (or is) supposed to be running on.  Lack of resource agent
(i.e. lack of ability to monitor) is not taken as an indication that
such a resource isn't running there.

On 6/8/2012 3:36 AM, Brad Jones wrote:
> I have a cluster with three nodes, A B and C.  A and B can basically
> stand in for one another; they run a DRBD master/slave set, and
> failure of A where most things run normally fires up services on B.
>
> C helps arbitrate quorum and runs Stonith plugins.  I've written
> location rules to prohibit most of the production services from
> running on node C.
>
> Problem is, the DRBD RA tries to monitor on node C, even though DRBD
> isn't even installed.  (It fails, helpfully, "not installed.")  I'm
> stuck with a slowly-incrementing failcount on C.
>
> When I give all services a default location rule and set
> symmetric-cluster="false", some of the resources stay running on A but
> most of the important ones stop.
>
> This was raised back in 2010 here:
> <http://oss.clusterlabs.org/pipermail/pacemaker/2010-April/005873.html>
> but I can't find much more about this issue on the web and there's
> only passing mention of it in the Pacemaker documentation.
>
> Bottom line: What's required to correctly configure a cluster with
> symmetric-cluster set to false?
>
> FYI I'm on pacemaker 1.1.6, heartbeat 3.0.5, on Ubuntu 10.04.
>
> Thanks!  Brad
> --
> Brad Jones
> Brad at Jones.name
> Mobile: 303-219-0795
>
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>
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-- 

Sincerely,
  Matthew O'Connor

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