From: Harm Ensing (ensin001@hdxh0e.unix.telecom.ptt.nl)
Date: Thu Jul 31 2003 - 09:09:24 EDT
Thanks to all those who replied.
A good pointer for seach with Google was 'DLT passes' and 'DDS passes'
(where 'passes' was the operative word for me).
This gave me several interesting documents with technical data which
I'm still reading.
The maximum number of passes (the passing of a spot on tape over the
read/write head) is the important number.
For DDS this is 2,000. This computes to about 100-150 uses (write
_and_ read) in streaming mode or about 75 uses in 'shoeshine'
(non-streaming) mode.
A DLT (8000) allows 1,000,000 passes. Depending on the method of use
(full or partial backup) this computes to about 20,000 uses.
Since we operate a weekly rotating backup-schedule this means that
DDS tapes should be replaced after two years and DLT's every
400 (!) years.
I should note that some documents mention a lower number of passes
for older DLT types, but I concluded that DLT's will last
a (human) lifetime.
-Harm Ensing-
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