[ClusterLabs] Booth ticket multi-site and quorum /Pacemaker

[Andrei Borzenkov]

On Thu, Feb 24, 2022 at 1:17 PM Jan Friesse <jfriesse at redhat.com> wrote:
>
> On 24/02/2022 10:28, Viet Nguyen wrote:
> > Hi,
> >
> > Thank you so so much for your help. May i ask a following up question:
> >
> > For the option of having one big cluster with 4 nodes without booth, then,
> > if one site (having 2 nodes) is down, then the other site does not work as
> > it does not have quorum, am I right? Even if we have a quorum voter in
>
> Yup, you are right
>
> > either site A or B, then, if the site with quorum down, then, the other
> > site does not work.  So, how can we avoid this situation as I want
> > that if one site is down, the other site still services?
>
> probably only with qnetd - so basically yet again site C.
>

The problem with multisite cluster is not quorum (which is not
actually needed to run pacemaker) but fencing. One site cannot take
over resources until another site is fenced and if another site is
completely down fencing does not work.

So qnetd does not really help here (except with suicide self fencing).
If network conditions allow, it is better to have iSCSI target on the
third site and use SBD disk heartbeat. Self fencing requires SBD
anyway.