[Linux-cluster] quorum handling

[Lon Hohberger]

On Tue, 2009-08-11 at 14:30 -0500, Paras pradhan wrote:
> I have a 3 nodes xen cluser under centos5.3 that host linux virtual
> machines. Node1 and Node2 got virtual machines but not on Node3. Node
> 3 is basically used when Node1 or Node2 goes down. This is working OK.
> Now when I turn off both  Node1 and Node2. Then quorum is dissolved
> and my cluser fails. I do not see any virtual machines in Node3 if the
> other 2 nodes die.
> 
> So, how to handle this situation? I need node 3 to be alive a working
> to host virtual machines when Node 1 and Node 2 is shut down.

1/3 is not enough to constitute a quorum; you will have to use a quorum
disk or some other method in order to allow a quorum of 1 (out of a
possible 3).

You could make that node a high weight (like 3 votes), but then when it
fails, the other 2 nodes will not be quorate.

The reason for this sort of operation is to prevent a split-brain:  If
the 1 node is alive and running virtual machines, and the other 2 nodes
come online but *cannot* talk to the already running node, they can
start up the virtual machines, causing data corruption.

-- Lon