Patent ID: 8140599

Claim:
A method of identifying nonreferenced segments in a first storage system and a second storage system including: inputting a first plurality of segment lists, wherein each segment list is associated with a first primary deduplicator and each first primary deduplicator is associated with a first storage subsystem; inputting a second plurality of segment lists, wherein each segment list is associated with a second primary deduplicator and each second primary deduplicator is associated with a second storage subsystem, wherein at least one first and at least one second primary deduplicator share a common storage subsystem; compiling a first union of the first plurality of segment lists, wherein the first union comprises each distinct segment in the first plurality of segment lists compiling a second union of the second plurality of segment lists, wherein the second union comprises each distinct segment in the second plurality of segment lists; comparing the first union to a first secondary segment list associated with a first secondary deduplicator to determine a first set of previously referenced segments that are no longer referenced on the first storage system; comparing the second union to a second secondary segment list associated with a second secondary deduplicator to determine a second set of previously referenced segments that are no longer referenced on the second storage system; outputting the first set of previously referenced segments that are no longer referenced; and outputting the second set of previously referenced segments that are no longer referenced.