I am not a Windows guy, I admit, but in our data center there are many Windows 2003 Server installations (32bit) and we are going to virtualize them.
Management's choice is VMWare vSphere 4 (ESX 4) but nevertheless I wanted to know how Sun xVM/Xen behaves compared to ESX. Forget all that nice Management tools offered by vmware, the only thing I was interested in is the performance feeling when actually using them.
The picture at the right (click on it to enlarge) shows the hardware list of the two "brothers": To the left you'll see the xVM DomU with paravirtualized disk and network drivers, to the right there's the vSphere ESX virtual machine with a paravirtualized SCSI disk device (and an IDE boot disk, you cannot boot in ESX from a paravirtualized disk).