vMotion Migration Question (CPU)

BoomAM · 8 Nov 2011 at 11:00

Hi,
Can anyone tell me if i'll have problems vMotioning/moving VMs between hosts if one set of hosts is Core based and one is Nehalem based?

Dont need tons of educating on how vMotion works and all that ;-)

Just want to know if the architectures are compatible.

Thanks in advance.

Laser402 · 8 Nov 2011 at 11:41

You will unless you enable VMware EVC Mode to the lowest level CPU you have, which basically levels the playing field on all CPU's in the cluster.

BoomAM · 8 Nov 2011 at 13:12

Thought so.
As im a little rusty, the EVC mode thats set, its set on the host/cluter level and not at VMs? So our 'old' VMs that were made on the 'Core' hosts would be able to goto the Nahelem hosts fine and visa-versa, as long as EVC mode was switched on?

What about if host's wernt clustered?

m4cc45 · 8 Nov 2011 at 13:39

If they're not clustered (shared storage / shared network) then you can't vMotion (it will fail the validation rule) - you can do a cold migration though.

EVC is set at the cluster level.

M.

BoomAM · 8 Nov 2011 at 13:40

m4cc45 said:
If they're not clustered then you can't vMotion - you can do a cold migration though.

EVC is set at the cluster level.

M.

I know if its not clustered i cant vMotion.

I meant as manual migrations. With EVC being a cluster level thing, can i manually move VMs between new and old hosts without issues?

Laser402 · 8 Nov 2011 at 13:41

As far as I'm aware the EVC mode is only set on clusters of hosts in vSphere (Not 100% sure). If you had 2 clusters both at the same level that would be fine. However I'm not sure what would happen if they were not clustered.

That said Core to Nahelem is gaining more features so all of this may be irrelevant and might 'just work'
I thought the only issue with vMotioning VMs was if they were going to a less capable host? Which meant they had to first be shutdown.

Are you going to be keeping the 'Core' Servers or just replacing?

mrbios · 8 Nov 2011 at 14:07

As far as I'm aware in order for a VM to move from one level of EVC to another, even if it's upwards you have to shutdown the VM first. I've heard/read you can do some funky stuff with CPUID masking or something in order to vmotion between hosts outside of a cluster but i've never gone into any detail on that.

You're right in that EVC mode is set at cluster level though.