vCenter Server performs a number of compatibility checks before allowing migration of running or suspended virtual machines to ensure that the virtual machine is compatible with the target host.

vMotion transfers the running state of a virtual machine between underlying ESXi systems. Successful live migration requires that the processors of the target host be able to provide the same instructions to the virtual machine after migration that the processors of the source host provided before migration. Clock speed, cache size, and number of cores can differ between source and target processors, but the processors must come from the same vendor class (AMD or Intel) to be vMotion compatible.

Migrations of suspended virtual machines also require that the virtual machine be able to resume execution on the target host using equivalent instructions.

When you initiate a migration with vMotion or a migration of a suspended virtual machine, the Migrate Virtual Machine wizard checks the destination host for compatibility and produces an error message if there are compatibility problems that will prevent migration.

The CPU instruction set available to the operating system and applications running in a virtual machine is determined at the time that a virtual machine is powered on. This CPU "feature set" is determined based on the following items:

Host CPU family and model

Settings in the BIOS that might disable CPU features

The ESX/ESXi version running on the host

The virtual machine's virtual hardware version

The virtual machine's guest operating system

To improve CPU compatibility between hosts of varying CPU feature sets, some host CPU features can be "hidden" from the virtual machine by placing the host in an Enhanced vMotion Compatibility (EVC) cluster.

Note

Host CPU features can also be hidden from a virtual machine by applying a custom CPU compatibility mask to the virtual machine, but this is not recommended. VMware, in partnership with CPU and hardware vendors, is working to maintain vMotion compatibility across the widest range of processors. For additional information, search the VMware Knowledge Base for the vMotion and CPU Compatibility FAQ.