A method of creating a synthetic backup set which can be used as a baseline for subsequent incremental backup or for the restoration of a data volume. The method includes copying a first data object from a first backup set to a memory media for storing the synthetic backup set, and copying a second data object from a second backup set to the memory media. The second data object is copied to the memory media when both the first and second backup sets are open for read access. In one embodiment, the first backup set data of data objects is stored on a first magnetic tape, and the second backup set data of data objects is stored on a second magnetic tape. When the second data object is copied to the memory media, the first and second magnetic tapes are simultaneously mounted on first and second tape drives, respectively.