I recently tried to implement Windows 2008 on an HP Integrity server and wanted to share a bit about my experiences. One of the things that Microsoft says is they support Windows 2008 on an Itanium box.
I was able to install Windows 2008 in Full installation mode on the Itanium box. The first thing I noticed is that there were only 2 roles available to me. I suppose I could install some Itanium based apps on the server and it would be good for that, but I couldn’t really use the box to do much else.
The other thing I noticed is that the much touted Windows 2008 Core mode installation is not supported on Itanium systems. As well there is no Hyper-V support on Itanium either. So realistically speaking, if you want to use a 64 bit system for Hyper-V you can’t use ia64, you are limited to x64.
So essentially unless you need to run something specific to Integrity servers you should stick with x64.