Enable EVC on running ESXI 4.1 cluster

[xbradshr]

I have a cluster of 13 ESXI 4.1, using E5540 intel processors. We plan to introduce a single X5675 host, with possibly more to follow.

I could enable EVC Nehalem(the highest available mode for E5540) for the existing 13 hosts, then introduce the new X5675 to the cluster. I am hoping this will allow EVC without downtime on the VMs.

I have been reading articles on enabling EVC. I am aware that raising EVC mode requires power on/off for the VMs to use the features, and that lowering requires the VMs powred off first.

-Does enabling EVC Nehalem on an initially identical cluster allow me to leave the VMs powered on?

-What if we decided to rollback, removing the X5675 and going from Nehalem to non EVC?

-one more thing, vcenter is a VM in the cluster we plan to upgrade, are there any issues with that?

Articles read

https://www.vmware.com/pdf/vsphere4/r41/vsp_41_dc_admin_guide.pdf

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=100576...

http://kb.vmware.com/selfservice/microsites/microsite.do?cmd=displayKC&docType=kc&externalId=1003212...

[chriswahl · Accepted solution]

For your cluster of E5540s, enabling EVC with the highest mode will not require any outage. As long as it validates in the EVC selection window, you're good to go. You can then add the X5675 host.

I always advise having EVC enabled to make adding hosts later easy. It does not cause any realistic performance hit.

vCenter will not have any issues with being in an EVC cluster.

Cheers.

[xbradshr]

Chris, thanks. My third point about disabling EVC(potentially for rollback). Is it the case that there is no impact to running VMs, but they may need a power off/power on for the changes to take effect? In our case, as EVC would already be operating at the hightest feature set for  the existing CPUs, would disabling EVC make any difference?

[chriswahl]

Disabling EVC should not have any impact on your cluster. What might happen is that any VMs on the newer CPU X5675 platform would need to be restarted to take advantage of the Westmere chipset.

The EVC prompts will be clear about any impact enabling/disabling EVC mode will have, and it won't let you make a change that requires a power on/off of the VMs. It's a fairly safe feature to work with.