Patent ID: 8539179

Claim:
A computer-implemented method, at least a portion of the method being performed by a computing system comprising at least one processor, the method comprising: creating a first backup of a set of data units at a first point in time; creating, at a second point in time, a representation of one or more data units in the set of data units that have been modified since the first point in time, wherein the representation of one or more data units that have been modified since the first point in time comprises: a first bitmap that indicates each data unit in the set of data units that has changed since the first point in time; a second bitmap that indicates a state of each data unit in the set of data units at the first point in time, wherein the state of each data unit at the first point in time indicates whether data is being stored in the data unit at the first point in time; a third bitmap that indicates a state of each data unit in the set of data units at the second point in time, wherein the state of each data unit at the second point in time indicates whether data is being stored in the data unit at the second point in time; creating, based at least in part on the representation of one or more data units that have been modified since the first point in time, a delta that comprises data for updating the first backup to a second backup by comparing the first, second, and third bitmaps, wherein the delta represents a difference between the state of the set of data units at the first point in time and the state of the set of data units at the second point in time, and the data for updating the first backup to the second backup comprises: at least one reference to a data unit in the first backup, the reference identifying a data unit that was present in the set of data units at both the first and second points in time; at least one data unit that was modified in the set of data units between the first and second points in time; using the delta to update the first backup to the second backup that comprises modifications made to the set of data units between the first and second points in time, wherein using the delta to update the first backup comprises updating data units in the first backup with the at least one data unit that was modified between the first and second points in time.