EVC level when adding hosts (performance question)

[lyngsie]

How do you handle EVC when replacing/adding new hosts with very recent CPU types?

My vSphere EVC has been at "Penryn" level since we added 3 hosts with Intel Xeon E55xx CPU's some years ago (environment had a couple of older hosts then, why Penryn was chosen). Now we want to add new hosts with E5-2670 CPU's in the pool with the Xeon E55xx CPU's (hosts).

According to this white paper (http://www.vmware.com/files/pdf/techpaper/VMware-vSphere-EVC-Perf.pdf) the conclusion is, that all in all there is no significant performance changes when keeping the older EVC levels while adding new CPU's (encryption mode is the only exception).

Is that the general experience - just keep the highest possible/compatible EVC level - performance will not degrade?

[john23]

As per the paper, Point is right: you will not observe any performance improvement with older EVC levels.

Latest processor can not use their capability since it will be masked to continue with older EVC level.

-A

[lyngsie]

Thank you. I did not directly ask for a performance improvement keeping older EVC levels. My question concerns the overall performance, when I add several hosts with most recent CPU's, but keeping the old EVC level. Will the new hosts be less efficient? I imagine not everyone replaces the whole pool of hosts, when they need to upgrade hosts with more recent CPU's.

[john23]

When you enable EVC, Latest processors mask some of the features as per the EVC level. New host will not be able to use the latest processor features.

Less Efficient can be only calculated when you check which latest processor features are going to mask when you enable EVC.

Ex:

A latest processor support NPT, which older processor doesn't support. In EVC environment, the processor feature will be masked to maintain the EVC level.

-A

[MKguy]

Is that the general experience - just keep the highest possible/compatible EVC level - performance will not degrade?

The question of performance impact has been discussed a lot more than it deserves and in my experience and as the paper shows (with only very rare exceptions), yes it will not usually not have any significant performance impacts. The rare cases like with AES-NI exist though, so consider your hardware and applications and then evaluate the tradeoffs in flexibility and performance to make your decision.

My take on this topic in general is:

https://communities.vmware.com/message/2314826#2314826

[lyngsie]

Thanks for both helpful answers. I feel more confident about EVC and adding new CPU/hosts to an existing environment.