[ClusterLabs] How to unfence without reboot (fence_mpath)

[Ondrej]

Hello Strahil,

On 2/17/20 11:54 AM, Strahil Nikolov wrote:
> Hello Community,
> 
> This is my first interaction with pacemaker and SCSI reservations and I was wondering how to unfence a node without rebooting it ?

For first encounter with SCSI reservation I would recommend 'fence_scsi' 
over 'fence_mpath' for the reason that it is easier to configure :)
If everything works correctly then simple restart of cluster on fenced 
node should be enough.

Side NOTE: There was discussion previous year about change that 
introduced ability to choose what happens when node is fenced by 
storage-based fence agent (like fence_mpath/fence_scsi) that defaults as 
of now to 'shutdown the cluster'. In newer pacemaker versions is option 
that can change this to 'shutdown the cluster and panic the node making 
it to reboot'.

> I tried to stop & start the cluster stack - it just powers off itself.
> Adding the reservation before starting the cluster stack - same.

It sounds like maybe after start the node was fenced again or at least 
the fencing was attempted. Are there any errors 
(/var/log/cluster/corosync.log or similar) in logs about fencing/stonith 
from around the time when the cluster is started again on node?

> Only a reboot works.

What does the state of cluster looks like on living node when other 
nodes is fenced? I wonder if the fenced node is reported as Offline or 
UNCLEAN - you can use the 'crm_mon -1f' to get current cluster state on 
living node for this including the failures.

> 
> Thank for answering my question.
> 
> 
> Best Regards,
> Strahil Nikolov

--
Ondrej Famera