Patent ID: 7350041

Claim:
In a computer system comprising a first storage system comprising at least one first storage device, a second storage system comprising at least one second storage device, and at least one communication link that couples the first storage system and the second storage system, wherein the at least one second storage device is slower than the at least one first storage device, a method comprising: (A) receiving, at the first storage system, a request to store a content unit, the content unit being identifiable by a content address that is computed, at least in part, from the content of the content unit; and (B) determining whether to store the content unit on the first storage system or the second storage system based, at least in part, on a pre-defined policy; and (C) when it is determined in the act (B) to store the content unit on the second storage system: storing the content unit on the first storage system; replicating the content unit from the first storage system to the second storage system; and deleting the content unit from the first storage system, wherein the first storage system stores at least two different types of content units including a content descriptor file (CDF) and a blob, wherein each blob is referenced by at least one CDF that includes metadata relating to the corresponding blob, wherein the content unit is a CDF that references at least one blob stored on the first storage system, and wherein the act of deleting the content unit from the first storage system further comprises acts of: determining if the at least one blob is referenced by another CDF; and when it is determined that the at least one blob is not referenced by another CDF, deleting the at least one blob from the first storage system.