VMWare: Expanding ESX farm – which CPU-type suits best?

I am planning to expand a VMWare ESX farm.

What are the requirements the new host has to fulfill.

To ensure the full functionality, especially for vMotion, the hardware of the new host needs to be compatible.
Most important is the CPU-type and the CPU-microarchitecture.

Is an Intel Nehalem chip compatible with an Intel Westmere?

You can read about which CPU-types go together and which restrictions apply on the VMWare webseite.

In my special case we used ESX hosts with Intel Xeon X5680 6-Core 3.33 GHz CPUs. In this Xeon CPU-family (Westmere) the first three figures (X56xx) of the description are crucial for the compatibility. Luckily, we could get servers with the following equipment: Intel Xeon X5687 4-Core 3.60GHz CPU – a CPU with X56xx designation.

If you are looking for compatible servers, the following VMWare website can be helpful:

http://www.vmware.com/resources/compatibility/search.php

On this website it you can easily find out which server of which manufacturer is delivered with which CPU.
I was looking for a HP Rackmount server with Intel Xeon X56xx CPU and found out that HP Proliant DL380 G7 is available with this CPU.

So it is pretty helpful if you want to prepare expanding esx farms.