[Pacemaker] RHEL/CentOS 6.4: corosync -> CMAN migration

[Stefan Förster]

Hello world,

according to [1] using the pacemaker plugin with corosync is
deprecated and will cease to be supported at some point in the future
(on RHEL!). Instead, the use of CMAN and running pacemaker as a
standalone service is recommended.

Now, unfortunately, the former (corosync with pcmk plugin) is exactly
what we are using on two fileservice clusters, so we need a migration
path with no downtime. I'm going to do some extensive testing later
this week, but I'd be grateful for a bit of advance help. I think what
I will try is:

1. Put pacemaker into maintenance mode.
2. Stop corosync, remove corosync.conf and the config snippet loading
   pacemaker from within corosync.
3. Install cman and ccs.
4. Generate new cluster.conf, using appropriate tools.
5. Start cman, start pacemaker.

The two crucial questions are:

1. In step (2), will pacemaker stop resources when it's brought down,
   despite being in maintenance mode?
2. In step (5), will the pacemaker resource configuration be
   preserved throughout this migration?

Any insights would be greatly appreciated.


Cheers
Stefan

[1] https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/6/html/6.4_Technical_Notes/pacemaker.html