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LTO Tape Characteristics

Wraps

  • LTO-8 12TB has 208 physical wraps, 6656 data tracks.
  • LTO-9 18TB has 280 wraps, 8960 data tracks.

What is the difference between physical wrap and logical wrap?

In LTO, physical wrap and logical wrap are the same.

In TS11xx they are different in that TS11xx processes wraps in logical order. Logical wraps follow the sequence of data processing, and there are many such sequences which vary based on FastSync, scaling, format type, and number of segments. Although logical wraps map to a fixed number of physical wraps defined by cartridge format, they can be shorter due to segmentation and so have a larger count than physical wraps.

LPOS Values

LPOS values are set by the media manufacturer during the creation of their tape pancakes. The beginning LPOS value on each cartridge will likely be different. The delta in min to max LPOS will be the same in each generation's cartridges, but may be different between generations.

Tape Directory

There is no HRTD (High Resolution Tape Directory) on LTO, these only exist for Enterprise drives (IBM TS11xx). However, the LTO tape directory includes counts for each half wrap (i.e., there is a count at the Half of Wrap and there is a count at the End of Wrap). This is from where we extract the information that populates the REOWP command (see 5.2.19 READ END OF WRAP POSITION - A3h[1Fh][45h] in the LTO SCSI Reference).