[ClusterLabs] pacemaker drbd resource speed

[Ken Gaillot]

On Wed, 2017-12-06 at 15:11 +0200, Vaggelis Papastavros wrote:
> Dear friends ,
> we have the following configuration setup ,
> 1. Corosync Cluster Engine, version 2.4.0 
> 2. Pacemaker 0.9.152  under CentOS7 .
> 3. DRBD version 9.0.8
> Everything is configured as clustered resource and is working fine.
> I need to make some changes on the DRBD resource configuration file,
> the corresponding resource is also a pacemaker resource 
> (i.e., everything managed by pacemaker) . 
> Please help me the recommended order of the above changes without
> down time .  

It's been a while since I used DRBD, so someone who knows more may
correct me, but for Pacemaker in general, you can make any changes you
want to a cluster by putting it into maintenance mode.

Exact syntax depends on your configuration tool but the result is
setting maintenance-mode=true in cluster properties.

In maintenance mode, pacemaker will still run and report the results of
monitors, but it won't start or stop anything. You can set maintenance
mode, make your changes, wait for all the monitors to come back clean,
then leave maintenance mode.

That approach leaves everything else running. If you have dependencies
that will fail if you make DRBD changes, I would set target-
role=Stopped on the DRBD resource in Pacemaker, which will make
Pacemaker stop DRBD and everything that depends on it. Then, you can
make your changes, start DRBD manually to test them, then stop DRBD and
re-enable it in Pacemaker so Pacemaker starts everything again.

> For example if i change the global_conf of DRDB configuration, what
> actions I need to make on the Pacemaker in order to reload the
> resource 
> with the updated values ?
> 
> Sincerely ,
> Vaggelis Papastavros 
-- 
Ken Gaillot <kgaillot at redhat.com>