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

Wed May 26 11:48:25 EDT 2021

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.    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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