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From: res@ihlpl.UUCP
Newsgroups: comp.unix.questions,comp.misc
Subject: Re: Re: Should we reuse mag tapes?
Message-ID: <1861@ihlpl.ATT.COM>
Date: Mon, 23-Feb-87 22:28:59 EST
Article-I.D.: ihlpl.1861
Posted: Mon Feb 23 22:28:59 1987
Date-Received: Fri, 27-Feb-87 20:41:53 EST
References: <1058@megatest.UUCP> <484@apple.UUCP>
Organization: AT&T Bell Laboratories - Naperville, Illinois
Lines: 34
Xref: utgpu comp.unix.questions:1176 comp.misc:283
Summary: It depends on the brand to some extent

In response to:

> >   The question is:  Is it safe to reuse mag tapes  for  important  data  or
> >   should we use brand new tapes when storing critical information?
> >
> >   Would someone have a strong feeling, based on experience or data, one way
> >   or  the other?  I know that the whole idea of using mag tapes is that you
> >   can reuse them a good number of times,  but  I  have  also  heard  people
> >   saying that valuable info should go on virgin tapes.
> 
> It takes a LOT of uses to wear a tape out.  I would guess somewhere in
> the hundred range or so...

While working on a tape controller for the AT&T 3B5 and 3B15 computers
we used one tape for soak testing for many days.  All told, I believe
it racked up on the order of 500 hours of use without exhibiting a
reproducible failure (we had to retire it when it got knocked from atop a 
machine and the reel ended up in three pieces.  The tape was Graham
Ultimag -- expensive, but it did the job for us very nicely.

On the other hand, our Lab Administration people once got a batch of
tape that the Purchasing Department must have got such a deal on.  Ten
passes over the head and the stuff was ready to be scrapped.  After
trying to use it for a short while they shipped it back to the
distributor and got some of the stuff that they ordered in the first
place.

So, how long a tape will last will depend on the initial quality 
(there are lots of good brands out there -- Graham being one of my
personal favorites, but not the only one by any means) and on the care
given the tape when you use it.

					Rich Strebendt
					...!ihnp4!iwsl6!res