Vmware EVC mode and mixed hosts

We're running a 4 host vSphere cluster with different generation HP Proliant hosts (G5 > G8) in EVC mode Penryn.

Can someone confirm that in EVC mode the cluster performance is "wound" back to the performance of the slowest host?  We think it is, or is it not that simplistic?

Cheers
kswan_expertAsked:
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MutogiIT ManagerCommented:
I have only used EVC in test, we went away from it when, in your case different Generations of servers are used.

you are correct in the fact the lowest, most compatible will be used as the 'Master' to ensure during vMotion the clients don't know they are moved.

One thing you can test is masking the CPU from the clients on ESXi, but it Will require a restart.

This may become an issue if the client is dependent on the mask to encrypt or decrypt data, the VM will have to be rebuilt from the ground up.
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AbhilashBloggerCommented:
I don't think the performance will be hit because EVC is not making the CPU perform slower.
The CPU works to its full potential but only the features that new processors had will be masked to math the lowest one's.
Can you confirm that the performance is related to CPU? have you ran any tests?
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kswan_expertAuthor Commented:
hi guys,

We don't have any performance issues.

I asked because we're putting together a business case for replacing the hosts and trying to explain why running G5 and G8s together is not ideal. I'll need to remove from the business case if not true- that it winds everything back to the lowest spec host.

I had a google for whether it (EVC mode) actually wound back performance but couldn't find anything that stated that, though I thought i'd read somewhere it did, hence the question.

Cheers
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AbhilashBloggerCommented:
You could tell that lot of new features that latest CPU's offer is masked because one or two servers are lower end ones.
Your business case to procure new servers is still valid. You just need to go from another angle.
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MutogiIT ManagerCommented:
Hit them with this:

Boss, If there is something i know is how to spend money in the manner to ensure when the next job comes across your desk your data that you need will be there.

OR

Boss, Im really good at my job and your really good at yours, let keep it that way...

OR

Boss, there are issue down the road with compatibility and running a mixed environment is not a good rule of thumb.


Honestly we have a mixed cluster, but we kept all the storage local for the (2) G5 and running a HP P2000 with (2) G8 8GB fibre and with the local storage we have 17 VMs about 30% CPU and the SAN has 37 VMware view clients at 22%. the G8's just push alot more data faster... about 30% more performance then G5 accross the board.
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