Enhanced VMotion Compatibility (EVC)

What is EVC?

EVC automatically configures server CPUs with Intel FlexMigration or AMD-V Extended Migration technologies to be compatible with older servers.

What is the benefit of EVC?

No. An EVC-enabled cluster only allows CPUs from a single vendor in the cluster. VirtualCenter and vCenter Server do not allow you to add a host from a different vendor into an EVC-enabled cluster.

What is the difference between EVC and the old CPUID masking feature (accessed from the Virtual Machine Settings dialog box, Options tab, CPUID mask option)?

vCenter Server does not permit the addition of hosts that do not provide support for EVC into an EVC-enabled cluster.

To use EVC, you must be running ESX 3.5 Update 2 or higher with VirtualCenter 2.5 Update 2 or higher and have compatible processors in your servers. EVC does not allow for migration with VMotion between Intel and AMD processors.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1005764

The older masking feature involved applying manual masks to individual virtual machines. EVC takes effect on a whole cluster and all virtual machines in the cluster. More accurately, EVC affects the hosts themselves, making all the hosts in the cluster appear to be the same type of CPU hardware, even if they are different.

What happens when a host is removed from an EVC-enabled cluster?

When a host leaves an EVC-enabled cluster, it reverts to its normal behavior. New virtual machines started on that host can access all the features of the CPU, and are not limited by the EVC mode that was in effect while the host was in the EVC cluster. Note that virtual machines that were once able to migrate to the host might no longer be permitted to do so.

Can I add an ESX/ESXi 3.5 Update 1 or earlier host to an EVC-enabled cluster?

No. EVC is supported only on ESX/ESXi 3.5 Update 2 and later.

Because EVC allows you to migrate virtual machines between different generations of CPUs, with EVC you can mix older and newer server generations in the same cluster and be able to migrate virtual machines with VMotion between these hosts. This makes adding new hardware into your existing infrastructure easier and helps extend the value of your existing hosts.

How do I use EVC?

EVC is enabled for a cluster in the VirtualCenter or vCenter Server inventory. After it is enabled, EVC ensures that migration with VMotion is possible between any hosts in the cluster. Only hosts that preserve this property can be added to the cluster.

After EVC is enabled for a cluster in the VirtualCenter inventory, all hosts in that cluster are configured to present identical CPU features and ensure CPU compatibility for VMotion.

Does EVC allow AMD and Intel CPUs to be VMotion compatible?

EVC is short for Enhanced VMotion Compatibility. EVC allows you to migrate virtual machines between different generations of CPUs.

Enhanced VMotion Compatibility (EVC) simplifies VMotion compatibility issues across CPU generations.