Dimitar
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Contributor

VMotion between 6 cores/4 cores ?

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Hi,

I have few DELL PE R900 (CPU - INTEL Xeon 7350- 4 cores) with ESX4 installed that are running in cluster (Vcenter4).

I want to join another PE R900, but this new Server has (CPU - INTEL Xeon 7460- 6 cores), and I still want to be able to VMotion between all Servers.

When I read article bellow seem that this is not possible, but I’m not sure if I’m reading it right. I cannot test it as server are at different location at the moment.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=100321...

Is anyone can give more info or some advice.

Thank you

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joshp
Enthusiast
Enthusiast

If I am understanding correctly I think you should be able to enable EVC on the cluster with the "Intel® Xeon® Core™2" baseline and both CPU types would be compatible for vMotion. Remember you can't have any VM's powered on in the cluster if you are going to enable EVC.

VCP 3, 4

www.vstable.com

VCP 3, 4 www.vstable.com

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joshp
Enthusiast
Enthusiast

If I am understanding correctly I think you should be able to enable EVC on the cluster with the "Intel® Xeon® Core™2" baseline and both CPU types would be compatible for vMotion. Remember you can't have any VM's powered on in the cluster if you are going to enable EVC.

VCP 3, 4

www.vstable.com

VCP 3, 4 www.vstable.com

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jadelzein
VMware Employee
VMware Employee

I agree with joshp -- this is not an issue as long as the cluster is EVC-enabled. ESX/ESXi is aware of the additional cores in the new server and will be able to address them accordingly. Once this is all setup, DRS should take advantage of the added resources and shift some of your workloads over (if enabled properly).

Jad

Dimitar
Contributor
Contributor

Thank you for the reply guys.

I read the article again and now I fully understand how it works. I was confused on first place.

I just have two follow up questions:

When I enable EVC for 'Intel xeon Core 2' and my Virtual Server is located on the Host with 6 Cores, when I VMotion to the host with 4 cores, basically I will not be able to get same performance that I get from the host with 6 cores. Correct?

Also when I enable EVC - this will not affect any performance in general in anyone of the hosts?

Thank you

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jadelzein
VMware Employee
VMware Employee

not necessarily true -- for example, if you have a 2-vCPU VM running on the 4-core host then migrate it to the 6-core host, the VM will still have access to at least 2 cores (assuming there aren't any resource constraints). the only reason you'll see better performance on the 6-core system is due to the higher performance processor or chipset.

when using EVC with "Intel xeon Core 2" setting, you are effectively masking any advanced features of the newer chipset and will be limited to the functionality of that EVC mode across all hosts in that cluster. so technically you can lose performance although i don't think it'll be anything noticeable at the VMs.

JE

Dimitar
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Contributor

Thank you jadelzein.

I understand now how it works.

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