Tuesday, January 29, 2008

One virtualization too many

Being so chuffed at converting all my physical machines to virtual machines I decided that maybe it was time to look at Virtual Server 2005 R2 as an option.

The good thing about Virtual Server 2005 is that it can use Virtual PC images directly which saves any messy conversions. The bad things are one - it has to go onto a Windows Server box (Virtual PC can go on Windows XP or Server) and it also needs IIS for its management console. It certainly does provide some additional flexibility but to my way of thinking makes things more complicated that I really wanted but hey I'll give it a go.

So I copied the existing virtual PC hard disk across from the original XP host machine, configured a new virtual PC in Virtual Server 2005 and bang the image was up and running. Wow, that was easy I thought. Maybe Virtual Server is the way to go? Everything seemed to be going along swimmingly until I began to notice a number of unexpected reboots of the newly created virtual PC. Then I started to get errors about disk corruptions and messages saying the virtual PC hard disk was locked and therefore the virtual PC wouldn't start.

Hmmm...what is the problem here? Thinking, thinking. Ah ha, noticed that most of the issues seemed to happen at the top of the hour. This was also was the time that our Shadowprotect was running creating image backups of our host machine hard disk. So it appears that Virtual Server 2005 machines don't like imaging software like Shadowprotect. My guess would be that this is because the virtual PC hosted by Virtual Server 2005 has no idea that an image is being taken and doesn't invoke Volume Shadow Copy. Thus the virtual server hard disk (apart from being HUGE) doesn't get 'frozen' by VSS and thus issues arise. Just my guess mind you.

So in the end I shut down the Virtual Server 2005 image, copied the virtual PC hard disk back to the original XP machine, fired up Virtual PC on the original XP Machine and then launched the original virtual PC (with the updated virtual hard disk - no other changes made). Guess what? It just powered up without any issues! Clearly another benefit of using Microsoft virtual technology (ie virtual hard disk inter-changeability).

So in my experience it appears that if you have Shadowprotect (or any other imaging disk software for that matter I suspect) and you are running virtual machines (again my guess is you'll see this whether you use Virtual PC, Virtual Server or VMWare) then you are going to have problems, that may lead to all sorts of virtual PC reboots and possible disk corruption. As I said I am not exactly sure of the specific cause but I am in the process of speaking to Storagecraft (the makers of Shadowprotect) about the issues.

You have been warned.