as Nick mentioned: if you have SVMotion licensed, i would recommend to use SVMotion.
with SVMotion you can even migrate the Exchange VM online. But its not as fast as when the vm is offline.
i would do it like this:
-present the second datastore to the ESXI server
-format at with VMFS5 and add it as a datastore
-rightclick the VM and say migrate -> change datastore -> selecht the new datastore and go for it
Clik here to view.
