Patent ID: 7941409

Claim:
A storage system comprising: a control unit in communication with at least one storage device, said at least one storage device storing data including one or more data units and corresponding metadata for each data unit, each metadata describing attributes of one of said corresponding data units, wherein said control unit is configured to calculate a first hash value based on content of each data unit and store the first hash value as part of the metadata corresponding to that data unit, wherein said control unit is configured to determine whether said data units should be compressed, and compress the data units when a result of said determination indicates the data units should be compressed, and wherein for each data unit that is compressed, said control unit is configured to calculate a second hash value based on content of that compressed data unit following compression and store the second hash value as part of the metadata corresponding to that data unit in addition to retaining said first hash value as part of the metadata corresponding to that data unit.