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Re: [Linux-cluster] How to disable node?



Jakov Sosic wrote:
On Mon, 31 Aug 2009 15:30:13 -0500
Alan A <alan zg gmail com> wrote:

You have to give your cluster 2 node setting on remaining two nodes.

How can I define a two-node cluster if a majority is needed to reach
quorum?

We had to allow two-node clusters, so we made a special exception to
the quorum rules. There is a special setting "two_node" in
the /etc/cluster.conf file that looks like this:

<cman expected_votes="1" two_node="1"/>

This will allow one node to be considered enough to establish a
quorum. Note that if you configure a quorum disk/partition, you don't
want two_node="1".

http://sources.redhat.com/cluster/wiki/FAQ/CMAN#two_node

Yeah I know how to set up two_node cluster, but didn't know that
reconfiguration is the only way out when one node is missing :( I'm
disappointed with this limitation, I hope that developers will sort it
out for RHEL6 :(

I don't see that there's anything to fix.  You had a three-node cluster
so you needed a majority of nodes up to maintain a quorum.  One node
died, killing quorum and thus stopping the cluster (the expected and
correct behavior). As a three-node cluster, it's dead. It can't be run as a three-node cluster until the third node is fixed. Those are the
rules.

A two node cluster requires special handling of things to prevent the
dread split-brain situation, which is what two_node does.  Running the
surviving nodes as a two-node cluster is, by definition, a
reconfiguration.  I'd say simply requiring you to set two_node is pretty
damned innocuous to let you run a dead (ok, mortally wounded) cluster.

If you pulled a drive out of a RAID6--thus degrading it to a RAID5--
would you complain because it didn't remain a RAID6?
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