[ClusterLabs] 8 node cluster

[Andrei Borzenkov]

On Tue, Sep 7, 2021 at 8:37 PM M N S H SNGHL <singhal.maneesh at gmail.com> wrote:
>
> Hello Team,
>
> I am looking for some suggestions here. I have created an 8 node HA cluster on my SuSE hosts.
> Have configured certain group resources on it, which mostly run on a single node.
>
> Everything works fine, but I am at a fix for certain requirements -
>
> 1) The resources should work fine even if 7 nodes go down, which means surviving node should still be running the resources.
> I did set "last_man_standing (and last_man_standing_window) option, with ATB .. but it didn't really work or didn't dynamically reduce the expected votes.
> 2) Another requirement is - If all nodes in the cluster go down, and just one (anyone) comes back up, it should pick up the resources and should run them.
>
> I tried setting ignore-quorum-policy to ignore, and which worked most of the time... (yet to find the case where it doesn't work).. but I am suspecting, wouldn't this setting cause split-brain in some cases?
>

Yes, the only way to do it is to ignore quorum and to resolve split
brain you must have working fencing/STONITH between nodes. This
applies to startup as well - if a cluster is incomplete, before
starting to manage resources missing nodes must be fenced.

It is not about "some case" - in general working fencing is necessary
even if you do not ignore quorum.

This means you may have race conditions on startup if nodes come up
with delay. But it is up to you to decide what is more important.