[Pacemaker] 2 Node Cluster: some principal questions

Lentes, Bernd bernd.lentes at helmholtz-muenchen.de
Thu Mar 22 14:04:14 EDT 2012


Andreas schrieb:
> 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.

Running vm1 and vm2 on node1 and vm3 and vm4 on node2 ?

> 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.

I thought that cLVM prevents data corruption, if two identical VM's access the corresponding lv simultaneously.
Ok, it does not.

I will have STONITH (HP ILO Network Adapter).


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