Just some more random ramblings.

I've been using XEN (the one included in SLES 10) for a while and it's fairly fast, but missing some features (like multiple snapshots, vmotion, etc.)

I have a little machine at home (one of those Shuttle "cube" thingies). SLES installed fine on it, but could never get the XEN kernel to load due to nvidia drivers (even with the nvidia open source drivers just didn't want to run).

Tried Vmware ESXi (even newest version 4). But it's VERY picky about hardware and won't install. (won't even install at half the actual SERVERS we have at work either).

Vmware ESX/Vsphere (the one you pay for) is great, but the performance, compared to XEN on SLES is poor, IMO.

So that lead me to Citrix XEN Server 5.5 (The free one). It actually installed on my little Shuttle. Para-virtualized performance is nice. However, a few things lacking:
a) You cannot install SLES into the XEN VM with a GUI enabled (but you CAN do this on SLES 10 XEN).
b) You must then install XEN "tools" (like in vmware) --but you don't have to do this with SLES XEN.
c) You can then only run VNC to get a GUI (you can't actually run any GUI for the VM if it's Linux, haven't tried Windows though). Not necessarily keen on that since it means you have to leave XEN Center open and logged in if you need to do something that will take a long period of time.
d) has same issues as XEN with CD/DVD booting, etc. (although a little easier to change it). Cannot "map" a CD drive that's on the workstation running XEN Center like you can with Vmware Vcenter.

But I can at least get snapshots and auto-starting of my VM's. I had vmware workstation on SLES which worked okay, albeit a little slowly, and there's no auto-start ability if you reboot the host machine (vmware wants for you to use their server/esx product instead).

Have to play more with it though. We shall see if I give up or try SLES 11 SP1 when it's out and see if I can get XEN to boot from there.