With server virtualization, things are definitely different. There are a lot of advantages, but things are very different when you are backing up virtual servers. What we are finding is the amount of data that needs to be backed up has increased significantly.
However, in some cases server virtualization can reduce the number of backup licenses. This is a nice benefit. You don't have to run as many agents as in the past, and you can save some money there.
In some environments, server virtualization has prompted the use of a secondary storage system, for example, a disk-to-disk backup system to maintain multiple copies of images.
Check out the entire Virtual server backup FAQ
