How VMware vSphere 5.x VAAI XCOPY is handled by EMC VNX platform.

It is not so obvious and hard to find how VAAI XCOPY is handled if we clone Virtual Machines between datastores which are not shared across esxi host or esxi clusters. Here is the answer:

In order for VAAI to work

The source and destination LUNs (Datastores) must be accessible by the host performing the clone task, and they must be on the same VNX storage system

You need to make sure that your host has source and destination datastores mounted or it will fall back to a host copy.

Here is link to excellent document of Jeff Purcel from EMC Engineering [h8229-vnx-vmware-tb]:

http://tinyurl.com/mggkf7o

Enjoy!