Comments on: VMware EVC cluster, what is that?

By: Johan

Johan — Fri, 10 Jul 2009 17:54:53 +0000

Thanks for your input. I implemented EVC a week ago, and have not encountered any problems with activating it or with the applications running on VM’s that are being VMotion’ed back and forth beteween what used to be incompatible CPUs.

By: Viperian

Viperian — Wed, 01 Jul 2009 09:36:30 +0000

In the real world experience three of the customers I gave advice on the matter have switched to an EVC cluster so they can hold as many ESX servers in a cluster. I would recomment to test the application on an EVC cluster if you arent totally sure the application is written cleanly. So just hope the application developer correctly used the CPUID to find out which instcructions to use in the application. If it is an application already running on the VMware cluster and you are adding two new hosts to it I would say go for it. If its a new application test it by creating an EVC cluster using 1 ‘old’ESX and 1 ‘new’ESX server.

Regards,
Edwin

By: Johan

Johan — Fri, 19 Jun 2009 06:35:51 +0000

Hi Vip,
I’m looking to implement EVC for one of our customers. This is because two of our hosts have SSE4-capable CPU’s, while the rest is only SSE3. I also read the article at http://hyperinfo.wordpress.com/2008/08/27/vmware-esx-and-enhanced-vmotion-compatibility/, which makes me concerned about the fact that EVC only “masks” the (in my case) SSE4 feauture. As I understand it, it’s still possible for applications to use feautures which are masked by EVC and this could theoretically result in unexpected behavior by applications, when a VM is vmotioned to a CPU which does not have (for example) SSE4.

What’s your take on this? Any real-world experience (good or bad) with EVC in these kinds of situations?

Regards,
Johan