Of Virtual PC differencing disks

People know I LOVE me some Virtual PC. But what I don’t love is the amount of disk space each image takes up.

I have a lot of virtual pc images on my main box “newton”. Now, I have tons of disc space, but that’s not the point. The point is that for each image, by default, there is 2+ GB of wasted space for the OS install.

Well, waste space no more. I found a great feature in Virtual PC call differencing disks. Basically, it allows you to define a parent hard drive for another hard drive. So, in my case, I have a windows xp default install as a parent hard drive. I can use that as the base for all my other windows xp installations, so as not to deuplicate the original OS install.

Aside form saving 2+ GB of disk space with every vm I create, I also avoid the while installation / activation of windows xp. I install it once, and that’s it. It’s very nice.

One of the downsides is that if you make any changes to the parent hard drive, it invalidated all the children of that parent. So it’s best to mark the parent hard drive as read only and go from there.

All in all, a nice way to save a TON of space.