[ClusterLabs] Hypothetical question: transitions slow in one direction

Reid Wahl nwahl at redhat.com
Fri Feb 11 21:31:26 EST 2022

On Friday, February 11, 2022, john tillman <johnt at panix.com> wrote:
> Hypothetically, if I have a two node cluster on identical VMs without
> fencing and I see transitions take longer in one direction than the other.
>  What are some possible reasons?
> For example, "pcs node standby nodeX" or "pcs cluster stop nodeX" results
> in a very fast transition to nodeY.  However, given the same commands but
> going from nodeY to nodeX takes much, much longer.
> And note that powering off either VM does *not* exhibit this behavior and
> transitions times in both direction are the same, fast.
> Best regards,
> -John

I'm assuming that in all cases, your resources are all running on the node
that you're stopping or putting into standby mode. Otherwise, it could be a
matter of "having to do work" versus "not having to do work."

With that said, it could be that the node that's acting as DC is slower to
stop or start resources than the non-DC node, because the scheduler and
controller daemons have to do more work there. Or it could simply be that
there are non-cluster-related workload differences between the two VMs.

- Reid
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Reid Wahl (He/Him), RHCA
Senior Software Maintenance Engineer, Red Hat
CEE - Platform Support Delivery - ClusterHA
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