[Pacemaker] 2 Node Cluster: some principal questions

Lentes, Bernd bernd.lentes at helmholtz-muenchen.de
Thu Mar 22 14:24:52 EDT 2012

Andreas wrote:
> On 03/22/2012 04:47 PM, Lentes, Bernd wrote:
> > Hi,
> >
> > thanks for the quick response. So the data is not destroyed if two
> > identicals VM's access the LV simultaneouslay ? I thought
> > it would be. I
> > will have stonith too.
> > What is about live migration ? Is it possible with my setup ?
> Well, if you want live migration you must _not_ use an "exclusive" vg
> but allow both nodes to access it simultaneously.
> It is also possible to balance the VMs across the nodes.

One further question. I plan to create only one vg for all LV's. Assume that some vm's are running on node1 and others on node2.
In my scenario they access the same VG. Is that a problem ?

> The most important part in your setup regarding data protection is a
> working STONITH setup ... and a correctly configured clvm
> setup will not
> allow a node to activate a vg and its lvs without consensus about the
> cluster state and it coordinates changes to the metadata but
> it does not
> coordinate concurrent access to the data.
> That is within the responsibility of Pacemaker to start VMs
> only on one
> node ... and Pacemaker relies on STONITH to be certain about
> node states.


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