[Pacemaker] 2 Node Cluster: some principal questions

[Andreas Kurz]

On 03/22/2012 07:04 PM, Lentes, Bernd wrote:
> 
> Hi,
> 
> 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.
> 
> Ok.
> 
>>
>> It is also possible to balance the VMs across the nodes.
> 
> Running vm1 and vm2 on node1 and vm3 and vm4 on node2 ?

For example, yes.

> 
>>
>> 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).

Works fine.

Regards,
Andreas

-- 
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> 
> 
> Bernd
> 
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