[ClusterLabs] 3 node cluster to 2 with quorum device

[Andrei Borzenkov]

06.01.2019 8:16, Jason Pfingstmann пишет:
> I am new to corosync and pacemaker, having only used heartbeat in the
> past (which is barely even comparable, now that I’m in the middle of
> this).  I’m working on a system for RDQM (IBM’s MQ software,
> clustering solution) and it uses corosync with pacemaker.  I set it
> up and had a 3 node cluster with resources available everywhere (any
> node could be made active).  However, we need to set this up as 2
> nodes as being available for the resources and 1 node to only
> function as a quorum device.
> 
> To try to accomplish this, I first banned the services from one of
> the nodes (pcs resource ban <resource> <node> and uninstalled those
> components from the node.

"pcs ban" is really intended for temporary moving resource off node; it
even has timeout parameter to cancel its effect automatically. You
should create normal location constraint if you want to permanently
exclude some node from being used for specific resource.

>  Now when I do pcs status, I get Failed
> Actions: * <resource_monitor_0> on node1 ‚not installed‘
> 

This is resource probe which is run one time when node is started;
pacemaker is using it to get informed which resources are currently active.

> Is there a „proper“ way to remove a resource from a single node?
> 

One possibility is to set resource-discovery=never or
resource-discovery=exclusive option on location constraint. Which one
depends on whether you use opt-out or opt-in cluster (i.e. whether by
default every resource can run anywhere or nowhere).

It may be possible to simply set node in standby mode, although I am not
sure whether probes are still run in this case.

Finally you can simply convert your cluster into two-node cluster :)
thus avoiding all these issues. What is the point of having the third
node if it won't ever run any resource?

> I did look up removing a resource from a specific node, but the only
> reference I could find was how to remove a resource from ALL nodes.
> Perhaps having the IBM tools create the cluster to begin with left me
> missing some fundamental knowledge I would have had if I did it from
> scratch, but for IBM to support our configuration, they require the
> use of their setup tools.  They don’t have any documentation on how
> to do a 2 node cluster with additional qdevice, so we’re on our own
> for this part.
> 

It sounds like you already modify configuration in incompatible way thus
possibly losing support.

> My apologies for not being able to copy/paste the text, but our
> system is air gapped and I have no way to do so.
> 
> Thanks for any help with this.
> 
> Jason Pfingstmann
> 
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