[Linux-cluster] Questions related to cluster quorum and fencing

[Parvez Shaikh]

Hi all,

*Quorum - *
The questions are bit theoretical, I have gone through documentation and man
pages and have understood that, a cluster is "quorate" if a cluster or its
partition has nodes, with votes equal to or more than "expected_votes" in
"cman" section of cluster.conf file (with no requirement mandating use of
quorum disk)

So how does cluster being quorate or non-quorate affects functioning of a
cluster or services? If cluster is non-quorate, does it indicate an alarming
situation and why?

If a cluster is composed of resource groups which including only IP resource
and script resource monitoring my application server listening on IP
resource(no shared disk or shared resource between cluster nodes), then is
cluster being "quorate" (or non quorate) important for services and/or
cluster?

*Fencing - *
Is fencing and cluster being quorate or non-quorate related? I tried one
experiment, wherein I removed "fencing" for cluster nodes and shutdown one
of the nodes in cluster. And I got message in /var/log/messages indicating
fencing failed for node, and service was not failed over from that node. So
is fencing mandatory even if there is no "shared" disk between two cluster
nodes?

Also is a cluster non-quorate in a time window when a node has failed and
has not been fenced successfully?

Yours gratefully
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