I've done this a couple times, and each time it's really been an "it depends" situation because it's *highly* dependant upon your storage vendor, your interconnect, and their specifications. So, I'm sure you've probably done this, but you really need to research this carefully with that VNX, read all the EMC docs, probably open a SR if you have any questions. From a vSphere perspective, it's fairly straightforward but you will need to make some HA tweaks to understand the vMSC topology. Several blogs on this as well as covered in the official docs. Overall, largest thing is to ensure you have adequate site interconnect, latency is low (what is it?), and you've done all the calculations to understand how this will/won't scale.
