IT administrators have traditionally backed up their physical servers with backup agents on each server, with the backup agent installed on top of the operating system (OS) running on the physical server. Each backup agent had its own physical server on which to run, and could access all the resources belonging to that physical server without undue concern for over-utilizing the physical server.

However, this old paradigm of using a single backup application agent on each physical server can break down with large numbers of virtual machines running on a smaller set of physical servers. With the adoption of server virtualization, where multiple guest operating systems now run on a single physical server, the traditional one-backup-agent-per-OS approach presents problems. Multiple guest OS's may now require multiple backup agents to be run on a single physical server, potentially taxing the resources of the physical server and therefore the resources available to all of the virtual machines and all of the applications running on those virtual machines, on that single physical server.

Server virtualization brings advantages in creating second-site server backups, since all that is required for a virtual server backup is a copy of the virtual server image. Server virtualization also increases storage utilization, as moving from physical to virtual servers and often results in a larger number of combined physical and virtual servers in the environment.