Tracy writes:
> For example, I daily append my spoolfiles to a
> backup tape using BackPack.  I can get about
> 45 appended spool file backups to a 90M DDS
> tape before it wants another one.  (I think
> the limit is 512 or 256 appends.)

The tapes will start to fall apart after 150 or so though.

HP rates its DDS tapes for 2,000 passes of the head over the tape, but you
will typically exceed this after 100-150 uses due to the fact that parts of
the tape are passed over multiple times, and if the tape does not continue
to "stream" then it will have to stop at which point the head spins against
the tape for a moment before stopping.

So about 75 uses seems to be a commonly recommended maximum for DDS tapes,
especially in cases where the conditions are less than perfect from a
temperature/humidity/handling point of view.

HP recommends using a cleaning tape weekly, but suggests avoiding
unnecessary use as the cleaning tape grinds down the heads and will
ultimately reduce the lifespan of the tape device itself.

> What bugs me in the back of my mind is, it
> BackPack "really" reporting a dirty tape or
> is it hitting a flag that says 10 or more
> rewinds means to report it as such?  This
> is because I think it increments a counter
> every time in his a new directory.

My guess is that this reflects some actual soft (recoverable) errors being
encountered when writing the tape, which may be an indication that your
tapes are starting to wear out sooner than you would like.  If you're going
to be doing multiple appends to a tape, I would think that getting the
highest quality DDS tapes would be especially important.

G.

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