starts at band 0, wrap 0, a forward wrap that runs from the beginning of the tape (BOT) to the end of the tape (EOT) and includes a track that runs along one side of the data band. The next wrap written, band 0, wrap 1, is a reverse wrap (EOT to BOT) and includes a track along the other side of the band. Wraps continue in forward and reverse passes, with slight shifts toward the middle of the band on each pass. The tracks written on each pass partially overlap the tracks written on the previous wrap of the same direction, like roof shingles. The back and forth pattern, working from the edges into the middle, conceptually resembles a coiled serpent and is known as linear serpentine recording. When the first data band is filled (they are filled in 3, 1, 0, 2 order across the tape), the head assembly is moved to the second data band and a new set of wraps is written in the same linear serpentine manner. The total number of tracks on the tape is (4 data bands) × (11 to 52 wraps per band) × (8, 16, or 32 tracks per wrap). For example, an LTO-2 tape has 16 wraps per band, and thus requires 64 passes to fill. Logical structure Since LTFS is an open standard, LTFS-formatted tapes are usable by a wide variety of computing systems. The block structure of the tape is logical so interblock gaps, file marks, tape marks and so forth take only a few bytes each. In LTO-1 and LTO-2, this logical structure has CRC codes and compression added to create blocks of 403,884 bytes. Another chunk of 468 bytes of information (including statistics and information about the drive that wrote the data and when it was written) is then added to create a "dataset". Finally error correction bytes are added to bring the total size of the dataset to 491,520 bytes (480 KiB) before it is written in a specific format across the eight heads. LTO-3 and LTO-4 use a similar format with 1,616,940-byte blocks. The tape drives use a strong error correction algorithm that makes data recovery possible when lost data is within one track. Also, when data is written to the tape it is verified by reading it back using the read heads that are positioned just "behind" the write heads. This allows the