This is where this gets most complicated!

I believe (and I could easily be wrong), that the tape is not written at
one time from front to back.  Instead,
it writes several tracks on a pass, then reverses, and writes more tracks
in a reverse pass.  it therefore
requries multiple passes across the entire tape to completely fill a tape.
If you completely completely
fill a tape the drive doesn't have to rewinde the tape since the last pass
is a reverse pass.

http://en.wikipedia.org/wiki/Linear_Tape-Open

Rick

"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU> wrote on 08/13/2008
09:24:04 AM:

> 1,000,000 passes @ 512 per week is about 37 years.  If I remember right
> an LTO4 is a 256 track serpentine tape, two complete writes per week is
> 512 passes.  We do not have many tapes that are fully written twice per
> week.  Shoe shining is only going to double the passes for that section
> of tape for that write, so maybe we get it down to 17 years for parts of
> the tape.  I hope to change tape technology before I reach 17 years.
> Or 1 full pass every week plus one extra pass every 11 days is about 42
> years.
>
> Andy Huebner


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