[Linux-cluster] Quorum Disk on 2 nodes out of 4?

Fabio M. Di Nitto fdinitto at redhat.com
Wed Nov 18 05:32:25 UTC 2009

Karl Podesta wrote:
> Hi there, 
> Is it possible to have a quorum disk, applicable only to 2 nodes
> out of a 4 node cluster?

No. The prerequisite for qdisk to work is for all nodes in a cluster to
have it running at the same time.

> This architecture should really be two clusters, right? One separate
> cluster for DB, and another cluster (even if) for the network apps?

Yes and no. By splitting the 4 nodes cluster in 2x2nodes clusters will
only help partially.

The cluster with qdisk will be ok because qdisk will act as tie breaker
for fencing/quorum, but the other 2 nodes cluster (for network services)
will require other kind of attentions to avoid fencing races.

> I gather it has been configured this way from a desire to logically
> keep all of these services together in the one "system". 
> Apologies if a similar question has been asked in the past, any inputs, 
> thoughts, or pointers welcome. 

Ideally you would find a way to plug the storage into the 2 nodes that
do not have it now, and then run qdisk on top.

At that point you can also benefit from "global" failover of the
applications across all the nodes.


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