Patent ID: 7441092

Claim:
A backup method comprising: calculating a set of new file record hashes; creating a list of potentially changed clusters based at least in part on comparing the set of new file record hashes to a set of previous file record hashes; calculating a set of current cluster hashes wherein each one of the set of current cluster hashes is calculated based on a corresponding one of a plurality of clusters of one or more storage devices, and wherein each one of the set of current cluster hashes uniquely identifies the corresponding one of the plurality of clusters, and wherein the calculating the set of current cluster hashes is based at least in part on the list of potentially changed clusters; reducing the set of current cluster hashes to include only those not already stored in a backup database, resulting is a reduced set of cluster hashes; and storing in the backup database a set of clusters of the plurality of clusters identified by the reduced set of cluster hashes wherein each cluster stored in the backup database is unique resulting in single-instance storage in the backup database.