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Re: [Linux-cluster] JBoss Clustering Compatibility

On Mon, 2006-08-21 at 14:13 -0400, Sutterfield, Geary L. wrote:
> Hello all,
> Does anyone have any information or experience about using GFS and the
> Cluster Suite and JBoss Clustering on the same cluster? I've been
> looking for a couple of days, but I can't seem to find any information
> on that configuration. Our goal is to create a J2EE cluster with a
> shared, global filesystem. GFS seemed like a logical choice. 
> I'm speculating that if Cluster Suite was only used for GFS, and not
> for any other services, then it might work okay with JBoss Clustering.
> Cluster Suite would handle the GFS clustering, and JBoss Clustering the
> J2EE app server clustering. But I also wonder about conflicts or
> incompatibilities. And I especially wonder how fencing would impact
> JBoss. Has anyone tried this configuration, or heard of anyone who has?

I have not tried it, but here are some of the 'gotchas':

(a) Disagreements in the JBoss cluster view vs. the GFS cluster view.
GFS cluster view should always win in the end, because it has fencing.
So, the GFS/RHCS cluster should be configured to converge on membership
changes before JBoss (whether that means increase deadnode_timeout, or
tweaking JBoss is up to you).

(b) Cluster quorum.  I don't know much about JBoss clustering (yet), but
remember that cluster suite / GFS need a majority of votes (normally,
there's a 1:1 correlation between nodes and votes) available in order to
form a quorum.  Without a quorum, access to GFS will be halted.

(c) Fencing.  You will probably need to use power-based fencing, because
storage/SAN level fencing will not drop a node out of the JBoss cluster
by itself.  Since I don't currently know much about JBoss clustering
generally, I also don't know the specific implications of trying to run
JBoss on a given node after the GFS volumes have been cut off from that
node.  I *assume* that JBoss would take that node out of the JBoss

> If there any problems, I suppose they will be worked out eventually,
> since Red Hat has acquired JBoss. But we don't want to waste a lot of
> time going down a path with known problems. Any thoughts or feedback
> would be appreciated.

-- Lon

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