Method and mechanism to distinguish valid from outdated recording blocks in a tape drive

A method of distinguishing old information from new information stored in a plurality of blocks in a medium, wherein a respective write pass count and a respective block identification are associated with each block of the plurality of blocks and a master write pass count is associated with the medium, the method comprising:

• reading the master write pass count, the plurality of blocks, the respective write pass counts, and the respective block identifications;
• comparing the respective write pass count and respective block identification of each block of the plurality of blocks with the respective write pass counts and the respective block identifications of a subset of blocks of the plurality of blocks in response to reading the subset of blocks of the plurality of blocks;
• accepting each block of the plurality of blocks where the respective block identification does not duplicate the respective block identifications of the subset of blocks in response to comparing the respective write pass counts and the respective block identifications;
• accepting each block of the plurality of blocks where the respective block identification duplicates the respective block identification of at least one other block of the subset of blocks, and where the respective write pass count is advanced as compared to the respective write pass count of the at least one other block of the subset of blocks in response to comparing the respective write pass counts and the respective block identifications;
• rejecting the at least one other block of the subset of blocks in response to comparing the respective write pass counts and the respective block identifications;
• and
• rejecting each block of the plurality of blocks where the respective block identification duplicates the respective block identification of the at least one other block of the subset of blocks, and where the respective write pass count is not advanced as compared to the respective write pass count of the at least one other block of the subset of blocks in response to comparing the respective write pass counts and the respective block identifications.