[Pacemaker] Live migration with order constraints

[Andreas Kurz]

On 11/10/2011 07:59 PM, Dmitry Golubev wrote:
>>>> Actually, it's called ManageVE. Well, I wonder what else an RA
>>>> could do other than manage :->
>>>
>>> ah, yes .. ManageVE ... thx 
>>
>> What I meant to say is that it's really hard to recall such a
>> name.
> 
> With all due respect, ManageVE does not have live migration. It just manages
> start/stop for a single virtual machine. What I need is to live-migrate a group
> of virtual machines which reside on one filesystem all together to a different
> node. Given that there might be more than one such group. Yes, it can be done
> having a resource for each virtual machine - i wouldn't object to that at all,
> but they must have live migration together with their underlying filesystem. I
> can't have cluster filesystem there, which could be mounted on both nodes and
> deliver the possibility to live-migrate everything without a glich or remounting,
> but unfortunately OpenVZ supports quotas only on ext2/3/4... so no OCFS or
> similar things for me :(

ManageVE has migration support using chkpt/restore since resource-agents
version 1.0.4. .... but if I understand the OpenVZ migration concept
correct ... please someone correct me if I'm wrong! ... there is no need
for a shared storage.

The vzmigrate script rsyncs complete data, config and state between
nodes .... no shared storage needed.

Of course you would need twice the diskspace, but this is also true for
DRBD replication. Extending ManageVE to use vzmigrate for live migration
looks quite straight forward to me.

> 
> My resource agent correctly does that thing with OpenVZ restart on the second
> node, but no live migration for now. Live migration (no matter, whether it is
> OpenVZ or KVM) depends on filesystem being either present on both nodes
> simultaneously (impossible with ext2/3/4) or unmounted/remounted (which requires
> order and location constraints). If there is no clean solution, is it really
> impossible to have one resource agent moving another resource (by issuing a
> commandline instruction to the cluster resource manager)?

So in fact you would only need to have two independent filesystems per
VM group running, one on each node with local storage.

Regards,
Andreas

-- 
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> 
> Thanks,
> Dmitry
> 
> 
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