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From: chris@mimsy.UUCP
Newsgroups: comp.misc
Subject: Re: Should we reuse mag tapes?
Message-ID: <5782@mimsy.UUCP>
Date: Fri, 13-Mar-87 09:43:31 EST
Article-I.D.: mimsy.5782
Posted: Fri Mar 13 09:43:31 1987
Date-Received: Sat, 14-Mar-87 10:24:39 EST
References: <1058@megatest.UUCP> <484@apple.UUCP> <2176@calmasd.GE.COM> <25773@rochester.ARPA>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 35

>>In the world of magnetic recording, unlike life, the first time is
>>not only the best, it's also completely forgettable.

In article <25773@rochester.ARPA> ken@rochester.ARPA (SKY) writes:
>That is what logic would lead one to expect and I agree with the
>reasoning behind this conclusion. However, my experience has been that
>running a new tape through the drive once, recording dummy data, makes it
>more amenable to recording the second time. I know, it doesn't make sense.

It makes sense if you change the base assumptions:

That new tape has been sitting in a warehouse for months, and has
been subjected to fairly large mechanical shocks (have you ever
watched truck loader at their task?).  Some of the oxide has been
loosened.  The first run through the tape drive `scrapes off' this
extra oxide.  (Try cleaning your tape heads immediately before,
and again after, running a new tape.)  This `oxide fluff' alters
the recording properties of the drive.  The second pass (after you
have cleaned the drive) is therefore more reliable.

A third set of assumptions:

The tape was wound under a different tension than your drive
generates.  This means that the first run through your drive changes
the `stretch' on the tape, loosening some of the surface oxide.
The second run through the tape drive `scrapes off' this extra
oxide, and so forth.

Another:

Make up your own!  It is easy and fun.  Cheap thrills!  But now
you have to test your hypotheses.  Step 1: find a fresh tape....
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
UUCP:	seismo!mimsy!chris	ARPA/CSNet:	chris@mimsy.umd.edu