[ClusterLabs] Quorum when reducing cluster from 3 nodes to 2 nodes

[Tomas Jelinek]

Hi Robert,

Can you share your /etc/corosync/corosync.conf file? Also check if it's 
the same on all nodes.

Dne 26. 05. 21 v 17:48 Hayden,Robert napsal(a):
> I had a SysAdmin reduce the number of nodes in a OL 7.9 cluster from 
> three nodes to two nodes.
> 
>  From internal testing, I found the following commands would work and 
> the 2Node attribute would be automatically added.  The other cluster 
> parameters we use are WaitForAll and LastManStanding.
> 
> pcs resource disable res_app03
> 
> pcs resource delete res_app03
> 
> pcs cluster node remove app03
> 
> pcs stonith delete fence_app03
> 
> Unfortunately, real world didn’t go as planned.   I am unsure if the 
> commands were ran out of order or something else was going on (e.g. 
> unexpected location constraints).   When I got involved, I noticed that 
> pcs status had the app3 node in an OFFLINE state, but the pcs cluster 
> node remove app03 command was successful.   I noticed some leftover 
> location constraints from past “moves” of resources.  I manually removed 
> those constraints and I ended up removing the app03 node from the 
> corosync configuration with “crm_node --remove=app3 --force" command.

This removes the node from pacemaker config, not from corosync config.

Regards,
Tomas

>     Now pcs status no longer shows any information for app3 and crm_node 
> -l does not show app3.
> 
> My concern is with Quorum.   From the pcs quorum status output below, I 
> still see Quorum set at 2 (expected to be 1) and the 2Node attribute was 
> not added.   Am I stuck in this state until the next full cluster 
> downtime?  Or is there a way to manipulate the expected quorum votes in 
> the run time cluster?
> 
> #17:25:08 # pcs quorum status
> 
> Quorum information
> 
> ------------------
> 
> Date:             Wed May 26 17:25:16 2021
> 
> Quorum provider:  corosync_votequorum
> 
> Nodes:            2
> 
> Node ID:          3
> 
> Ring ID:          1/85
> 
> Quorate:          Yes
> 
> Votequorum information
> 
> ----------------------
> 
> Expected votes:   2
> 
> Highest expected: 2
> 
> Total votes:      2
> 
> Quorum:           2
> 
> Flags:            Quorate WaitForAll LastManStanding
> 
> Membership information
> 
> ----------------------
> 
>      Nodeid      Votes    Qdevice Name
> 
>           1          1         NR app1
> 
>           3          1         NR app2 (local)
> 
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