1. A method of backing up a system image comprising: receiving a request to perform an initial backup of a first system image on a first computer system onto a server; determining whether a similar system image with a similar profile to the first system image is available from a catalog of system images; upon a positive determination, selecting the similar system image from the catalog of system images; identifying a first set of differences between the similar system image and the first system image; backing up the first system image by transferring the first set of differences to the server; receiving a request to perform an initial backup of a second system image on a second computer system onto the server; determining whether a second similar system image with a similar profile to the second system image is available from the catalog of system images; selecting the second similar system image from the catalog of images; identifying a second set of differences between the second similar system image and the second system image; and backing up the second system image by transferring the second set of differences to the server.