[Pacemaker] benefits of cman?

[Andrew Beekhof]

On Fri, May 18, 2012 at 7:17 AM, Matthew O'Connor <matt at ecsorl.com> wrote:
> Hi again!  I have a hopefully-quick question.
>
> As I've been experimenting with upgrade paths, and also from reading the
> Pacemaker Explained document, I understand that cman is either becoming
> required (per the Ubuntu upgrade path to 12.04) or is considered
> essential (per Pacemaker Explained).

cman will not become required.
In fact, depending on your distro+version, it is being phased out and
the membership+quorum services it had will be provided directly by
corosync 2.0.
This change is starting in fedora and its derivatives with f-17.

However, for distros+versions that have traditionally shipped RHCS
(fedora prior to f-17 and existing RHEL/CentOS/EPEL/... releases) it
/is/ recommended to keep using cman, since it is likely to have had
more testing, and to layer Pacemaker on top.
This is particularly so if you want to use cluster file systems such
as GFS2, since the utilities they need only understand cman.

Does this help?

>  Are there any detriments to using
> cman?

You saw this one?
  http://www.clusterlabs.org/doc/en-US/Pacemaker/1.1/html/Clusters_from_Scratch/_adding_cman_support.html

There is also additional information in:
  http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6-Beta/html/Cluster_Administration/index.html


> If I want to add additional nodes to the cluster, will I need to
> bring down the whole cluster or restart services on existing nodes to
> apply the new cluster.conf?

I don't believe so.  I think you need the 'cman_tool join' command.