Simply put, VSS allows you to create live snapshot backups of virtual machines while they are running. Previously, if you wanted to backup a virtual machine you had to bring it offline, back it up, and the restart it. This was one of the sole reasons a lot of organizations avoided virtualization technology completely. If your organization is holding back on Virtual Server because of the inability to do online backups then now would be a good time to reexamine that.
Chris Sanders is a network consultant for KeeFORCE, one of the most popular network consulting firms in western Kentucky. Chris is the author of the book Practical Packet Analysis as well as several technical articles. His personal website at www.chrissanders.org contains a great deal of information, articles, and guides related to network administration, network security, packet analysis, and general information technology.