[Pacemaker] Very strange behavior on asymmetric cluster

Arthur B. Olsen ABO at ft.fo
Tue Mar 15 18:10:59 EDT 2011

Tann 3/14/11 8:33 PM skrivaði "Pavel Levshin" <pavel at levshin.spb.ru>:

>14.03.2011 23:07, Arthur B. Olsen:
>> If a mysql server is running on a cluster node which is not defined to
>> run the mysql resource, pacemaker will mark it unmanaged and will not
>> start it on the node which it is suppose to run on. Same goes for
>> nfs-common. On my nfs servers nfs-common and nfs-kernel-server
>> resources should be running, and all others have nfs-common installed.
>> So pacemaker will just pick one random node marking the nfs-common
>> resource as running unmanaged and will not start it where i
>> specifically told it to run.
>> Likewise i can not have two drbd raid on different pair of node with
>> the same name. My two nfs servers hava a drbd raid between them and my
>> mysql servers hava a drbd raid running between them. Both had their
>> resources called r0 and pacemaker one to be slave and one to be
>> master, completely disregarding my location rules. Same with the mount
>> point. I can't use the same folder name  on both sql and nfs server to
>> mount the drbd0 disk in, because pacemaker will concider it mounted
>> and not try to mount the second. Changing the names of the resources
>> and the mount point solved the drbd issues.
>> Right now a mysql process is running as test on a web server in the
>> cluster, and pacemaker will not start it on my sql servers, same for
>> my nfs servers.
>> What i dont understand i why is pacemaker trying to monitor service on
>> nodes that are not supposed to run the service. And why does it stop
>> the service on the node that are supposed to run the service.
>Resources come unmanaged because you have fencing disabled and resource
>agent fails to "monitor" and "stop" on some node where it is not needed
>at all.
>You have not a way to tell the cluster that it is not supposed to run a
>service on some nodes. I believe this is a pacemaker's deficiency.

I thought that symmetric-cluster=true was exactly that.

>Currently, you have two ways:
>1. Delete resource agents from those servers which are not supposed to
>run it.
>2. Or make sure those "unused" resource agents return 5 "not installed"
>for monitor action. If they return anything else, you have your trouble.
>You may also divide your cluster into two or three independent clusters,
>one per resource group.

And so i did. Just made it tow independent clusters one for mysql, and one
for nfs.

Somewhat dissapointed that it didn't work. Seems like a better design to
have all in one cluster, for qourum and to share failover for some
resources like dns.

I still don't understand why it monitors services by default on all nodes
when the cluster is assymetrical

>Pavel Levshin
>Pacemaker mailing list: Pacemaker at oss.clusterlabs.org
>Project Home: http://www.clusterlabs.org
>Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf

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