Enable EVC in vSphere 5.5 without downtime

Hi Experts,

I need to enable EVC in my production VMware cluster since we bought three blade servers with different CPU version. Will it be possible to enable EVC in cluster without shutting down existing VM Guest OS. Actually I am trying to avoid downtime, at the same time if I enable EVC in cluster, does it have any negative result that might impact Guest OS. Appreciate if you please give me any reference link that might help me to understand the details.
ipsec600Asked:
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AbhilashBloggerCommented:
EVC basically enables the servers to have a baseline among them taking the least CPU functionalities from one of the server. You can't enable EVC on an existing cluster. You'll have to create a new empty cluster and then enable EVC and then move the hosts. I would suggest a reboot for VMs as they will move from a CPU of one functionality to another.
Detailed steps regarding enabling EVC is given in the below KB

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1013111
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
You will need to shutdown some VMs.

Normally, you would enable EVC on the Cluster first, but you will find, you can move VMs around, and move Hosts in and out of Cluster without affecting VMs, but finally, you will be left with a handful of VMs on a host.

and you will have to shut them down!

You cannot apply a CPU change to a VM, whilst it has the CPU in host.

So I'm afraid schedule downtime is required.

I need to enable EVC in my production VMware cluster since we bought three blade servers with different CPU version. Will it be possible to enable EVC in cluster without shutting down existing VM Guest OS.

I'm afraid this will require VM shutdown.

Will it be possible to enable EVC in cluster without shutting down existing VM Guest OS. Actually I am trying to avoid downtime, at the same time if I enable EVC in cluster,

VMs need to be shutdown.

does it have any negative result that might impact Guest OS. Appreciate if you please give me any reference link that might help me to understand the details.

Interesting you ask this, because VMware often does not let you know that EVC is a compromise, you've purchased new servers, with newer generation processors, with new instruction sets, and when you implement an EVC baseline, you are effectively TURNING OFF all those new fancy features in those host processors....

It's certainly possible it could impact Guest OS, if and only if, you require those instructions or features in the Guest OS....

see this Web Link for more details...

http://www.derekseaman.com/2012/09/how-much-does-evc-mode-matter-and-which.html

VMware have written a whitepaper called

Impact of Enhanced vMotion Compatiblity on Application Performance.

Some of our clients, decide NOT to use EVC and mix old and new servers, (e.g. old and new CPUs), because Apps and Guest OS will not benefit from these newer instruction sets.

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ipsec600Author Commented:
Thank you Guys for the details insight of this issue and apology for replying late.
I am now following the below procedure:

I  have created a new empty cluster and then enable EVC and then move the two same CPU compatibility EXi hosts on to this cluster and notice some networking issue and which is fixed now.
Shutdown guest OS and moved some less critical system into the new cluster and everything is working perfectly.

Now I will move one of the ESXi hosts(which is different CPU version) into the new cluster to see any issue and start moving Guest OS gradually, but for moving Guest OS, I am shutting down the VM and moving it.
Thank you once again.
ipsec600Author Commented:
Thank you for providing me the detail insight, you guys are Awesome!!
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