[Pacemaker] 2 Node Cluster: some principal questions

Andreas Kurz andreas at hastexo.com
Thu Mar 22 17:04:23 EDT 2012

On 03/22/2012 07:24 PM, Lentes, Bernd wrote:
> 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 ?

No, one vg is fine.


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>> 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.
> Bernd
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