During my internship I had to test against different kinds of products, and to be sure everything worked on a clean install of this product, I had to create multiple virtual PCâ€™s. One method of doing this was to create one clean Windows 2003 installation inside Virtual PC and copy this image to a new folder for every different server I needed. This was the method I started with, but one disadvantage was that it required a lot of disk space, as the base image already required 1.8 GB.
A solution to this problem was to use a feature of Virtual PC, called Differencing Disks. This allows for the creating of a base read-only image, which is called the parent, which can be shared with unlimited other virtual machines, the children.
Every child stores their disk changes in a separate file, making it possible to have one clean Windows 2003 parent image, and having a child which only adds Windows SharePoint Services to a separate file. The combination of parent and child would then become a Windows 2003 machine running Windows SharePoint Services.
This way, having a lot of different children uses a lot less space than having to copy the complete base image each time.
Additionally this method also can be used on a network to provide complete base images to all network clients. Making it possible to create an archive of base images for each platform (Windows 98, 2000, XP, 2003, Linux, BSD, â€¦) and placing them on a read-only network share, ready to be consumed by all users creating their own local child disks.