Bad tapes again!!!!

[Bob Green]

In article <9009192232.AA23148 at mcirps2.med.nyu.edu>, karron at MCIRPS2.MED.NYU.EDU writes:
|> I too have had bad tapes from sgi. I usually end up getting a new tape from
|> them. Still, don't they try to re-read the tapes, or otherwise verify tapes
|>  after they make a copy ?
|> 
|> dan.
|> +-----------------------------------------------------------------------------+
|> | karron at nyu.edu                          Dan Karron                          |
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Each tape that is produced by SGI or its vendors is rewound and read for data consistency.
On a sampled basis tapes are moved from one drive to another to verify tape drive head
alignment.  Our current research shows one cause above all others in contributing to
tape read errors.  We have found that foreign material on the tape drive heads will increase
the probability of read errors.  In most cases this results in recoverable errors which just slow
the read process.  In a few cases it results in unrecoverable tape read errors.  The solution in all cases
is to clean the tape drive heads.  We have included a request in our installation
instructions for users to clean their drives BEFORE attempting installation.

In a few cases (0.01% of tapes produced) we find that even with a clean tape drive that there is an
actual tape error.  We are researching these to find what in our processes could be causing this.

A third possibility is that the tape drives were not calibrated correctly when manufactured.
Although we have not seen evidence of this, we are keeping our ears open.

Bob Green
Software QA Mgr
Silicon Graphics, Inc
(bobg at sgi)
(415) 962-3438