Patent ID: 8504528

Claim:
A method comprising: storing, on at least one data storage device, blocks of data and first signatures of data chunks of each stored data block, the first signature of each data chunk including a reference to a storage location of the data chunk within a stored data block, the stored data blocks including data blocks of previous and recent backup sessions; storing, on the at least one data storage device, second signatures in a second signature repository, the second signatures calculated based on determined boundaries of the first signatures from previous backup sessions, at least one second signature being a signature calculated based on at least two first signatures of corresponding data chunks; and identifying data chunks of the recent backup session present in the stored data blocks prior to the recent backup session, the identifying including execution of instructions on at least one computer processor to perform data processing including: calculating, with regard to the recent backup session, second signatures based on determined boundaries of current first signatures of the recent backup session, at least one second signature calculated based on at least two first signatures of corresponding data chunks of the recent backup session; performing a search of the second signature repository for the calculated second signatures of the recent backup session to identify second signature matches; when a second signature match is not found, adding the unmatched second signature to the second signature repository; when a second signature match is found, writing data to an update file on the at least one data storage device, the data written to the update file identifying that the data chunks represented by the matched second signature are already present in the stored data blocks and storing the update file, the update file enabling a further process to remove duplicate data chunks from the blocks of data stored on the at least one data storage device.