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

[Nicolas Ecarnot]

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,

-- 
Nicolas Ecarnot