[ClusterLabs] Upgrading an Ubuntu 18.04 failover System

[Ken Gaillot]

On Wed, 2023-02-01 at 09:02 +0100, hajo.locke at gmx.de wrote:
> Hello,
>  
> 
> 
> > While the Pacemaker versions support rolling upgrades, those
> Corosync
> > versions do not, so you'll have to do the detach-and-reattach
> method.
> 
> > The main reason to do a new cluster instead is if you want to do
> some
> > testing before making it live.
> > --
> > Ken Gaillot <kgaillot at redhat.com>
>  
>  
> thanks for your answer.  So upgrading detached nodes will result in
> downtime of haproxy and may disclose some  other surprises...
> I think building a new cluster is the best way to avoid downtimes. In
> my case i could switch by DNS to new clusterservers and achive a
> mostly seemless transition of use.
>  
> Thank you,
> Hajo

The DNS transition is a good plan since it gives you a chance to do
some testing beforehand. (It's a good idea to lower the TTLs on your
DNS records to something like 1 hour, at least as far ahead of time as
the current TTL value.)

However I don't think there would be any downtime with a detach-and-
reattach. Only Corosync and Pacemaker are stopped in that scenario, all
other services remain running in an unmanaged mode.
-- 
Ken Gaillot <kgaillot at redhat.com>