Review: Xensource Xenserver for Windows

Xen and the art of server virtualisation

It has taken a while, but open-source Xen virtualisation technology is now available as a ready-to-run package that can be used to host Windows as well as Linux virtual machines.

As such, it could be considered alongside more established virtualisation products from Microsoft and market leader VMWare. However, the new Xenserver is quite different and, on this first showing, nowhere near as capable or polished as the competition.

You can’t just order a copy of Xenserver. It must be downloaded from the Xensource website and it’s pretty massive – 650MB.

That’s because it comes in the form of a CD-Rom image which, once downloaded, needs to be burned to a bootable installation CD or copied to a TFTP server for network deployment.

You then have to install the main Xenserver Host component, but unlike VMWare or Microsoft’s Virtual Server, Xenserver doesn’t run as an application under an existing host OS. It has to be installed from scratch onto a bare system. The Xen Hypervisor then runs natively to provide, supposedly, better performance and flexibility than hosted solutions.

The install procedure is semi-automated and much like installing Linux, mostly because that’s what you’re doing: installing a modified Debian Linux (used for its driver support) plus the Xen Hypervisor.

Most industry-standard processors, storage subsystems and network adapters will be identified and configured automatically, although compatibility isn’t guaranteed and problems could arise on older platforms.

We used a Dell Poweredge server with an Intel Xeon processor, but AMD is also supported. Another big difference from other virtualisation products is the need for processors with support for Intel VT or AMD-V hardware virtualisation technologies.

Other applications will use this if they can, and Xenserver will get by without if you only want to run Linux, but it’s essential for Windows virtual machines.

Xenserver is also particular when it comes to the versions of Windows it will host. The only choices are Windows XP with SP2 or Windows Server 2003, although this can be either the Standard or Enterprise edition with support for SP1 and R2 implementations.

Only 32-bit Windows can be used and, at present, there’s a limit of one virtual processor and 2GB of memory per VM. You’re also limited to eight concurrent virtual machines.

Guest operating systems are installed in the same way as on a physical server and the same licensing restrictions apply.

To manage Xenserver, you have to install a Java-based management console on another network PC. You must then connect to the remote server to create new virtual machines, start and stop them and so on.

You can tweak allocated resources (the virtual machine has to be stopped), check performance and connect to the remote console via an integrated VNC tool or, on Windows guests, Remote Desktop. Tools to convert existing physical servers into virtual machines are provided.

We had no real problems with Xenserver, but we didn’t find it as easy to configure or manage as rival products, such as VMWare Server. Neither did we see a huge benefit in terms of performance, getting similar results with the benchmarks we ran.

It also requires a fair amount of technical expertise and, in its current format, is not likely to threaten VMWare or Microsoft alternatives, especially as a small-business solution.