[ClusterLabs] Pacemaker and Corosync versions compatibility

[Ken Gaillot]

On 06/24/2016 08:46 PM, Maciej Kopczyński wrote:
> Hello,
> 
> I've been following a tutorial to set up a simple HA cluster using
> Pacemaker and Corosync on CentOS 6.x while I have noticed that in the
> original documentation it is stated that:
> 
> "Since |pcs| has the ability to manage all aspects of the cluster (both
> corosync and pacemaker), it requires a specific cluster stack to be in
> use: corosync 2.0 or later with votequorum plus Pacemaker 1.1.8 or later."

That's incorrect -- pcs has supported RHEL 6 and its derivatives (with
corosync 1 and CMAN) since at least 6.5. Thanks for bringing it up; I'll
delete that note.

> Here are the versions of packages installed in my system (CentOS 6.7):
> pacemaker-1.1.14-8.el6.x86_64
> corosync-1.4.7-5.el6.x86_64
> 
> I did not do that much of testing, but my cluster seems to be more or
> less working so far, what are the compatibility issues then? What will
> not work with corosync in version lower than 2.0?

corosync 2 is a cleaner implementation and has better message delivery
guarantees, but most of that is transparent to the user. With corosync
1, pacemaker will use a "legacy" version of the node attribute daemon,
so the attrd_updater command has fewer options. Most of the other
differences are in implementation, and may be less efficient for
example, but are not readily visible.

> Thanks in advance for your answers.
> 
> MK