[ovirt-users] Lowering cluster CPU level : safe?

[Itamar Heim]

On 06/17/2014 01:07 PM, Nicolas Ecarnot wrote:
> Hi,
>
> I'm trying to add some Westmere hosts into a Sandybridge cluster, and of
> course, they get refused :
>
> "Host xxxxxxxxx moved to Non-Operational state as host does not meet the
> cluster's minimum CPU level. Missing CPU features : model_SandyBridge"
>
> I tried to lower the cluster level but I get this warning :
> "Change Cluster CPU level
> There are running VMs. Lowering the Cluster CPU level might prevent
> migration of these VMs to some of the Hosts in the Cluster. Are you sure
> you want to continue?"
>
> As a frightened chicken, I clicked "Cancel" and turned to you : how safe
> is it to lower the CPU level?
> I understand some instructions will be missing, and maybe performance
> will change, but we don't have heavy CPU usage yet, so this may not be a
> big issue.
> I was wondering what will happen to my existing VMs?
> Will I have to modify some setup?
> What may prevent migration between westmere and sandybridge hosts?
>
> Regards,
>

(assuming not relevant, but for next person googling...)
live migration of VMs may fail / misbehave in such a case. we do not 
currently check the original cpu level to compare it during live migration.