[Linux-cluster] use of quorum disk 4u5 does not prevent fencing after missing too many heartbeats

[Lon Hohberger]

On Sat, 2007-12-01 at 15:21 +0100, Ferry Harmusial wrote:
> Hello All,
> 
> When I use a quorum disk in 4u5 it does not prevent fencing after
> missing too many heartbeats.

That's correct.

> http://sources.redhat.com/cluster/faq.html#quorum

I should clarify this answer (esp because I probably reviewed it).  It's
not quite accurate:

(A) Basically, it does kind of the contrapositive of what is mentioned
in the answer with regards to advertising / checking:

* We check our own fitness for participation in the cluster and
advertise it to the other nodes via the quorum disk.

* In the event of a failure, heuristics - instead of votes or a
race-to-fence - can be used to determine the quorate partition (and
therefore the partition that fences the other partition(s)).

(B) Nothing which currently ships with linux-clluster allow multiple
cluster partitions to continue running (like RHCS3 did) after a split.
With correct heuristics, one partition will always win - and fence the
other partition(s).


I apologize for the confusion. (Note: RHCS3 will continue running w/o
fencing, but in a degraded state; you cannot move around services or
alter the configuration safely while the cluster is split...)


The qdisk(5) man page (sections 1 & 2) has an explanation of how qdiskd
works.

-- Lon