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From: mfineman@cadev6.intel.com (Mark Fineman ~)
Newsgroups: comp.periphs
Subject: Re: What is the life-time of magnetic tape?????
Keywords: magnetic tape
Message-ID: <1912@inews.intel.com>
Date: 20 Jan 91 04:21:46 GMT
References: <1991Jan17.183902.24474@watdragon.waterloo.edu> <2337@shodha.enet.dec.com>
Sender: news@inews.intel.com
Reply-To: mfineman@cadev6.UUCP (Mark Fineman ~)
Organization: Intel Corporation, Santa Clara, CA
Lines: 51

In article <2337@shodha.enet.dec.com> devine@shodha.enet.dec.com (Bob Devine) writes:
 ...
> 1. environment of storage
>    - extreme temp swings are bad
 Yes, but I had 40 tapes stored in my unairconditioned apartments for
 7 years, followed by 10 years of storage in an unheated public storage
 place in San Jose and found no errors when I read the tapes, which
 were recorded at 1600BPI.

 However, I would still store anything I really care about in an
 air conditioned environment.
>...
> 2. number of uses
>    - tapes can last fine through up to 500 uses if handled correctly
 Most vendors claim 100K+, some 1000K+
>...
>two to five years.  The only sure gauge of tape reliability is the
>number of errors a tape generates -- a couple dozen recoverable errors
>is acceptable, hundreds of errors mean it is new tape time.
 I'd say 8 errors while writing the tape without backspace and rewrite
 (this is what VMS backup does) means:
  1. clean the drive,
  2. make another copy of the data (fix drive if any problems),
  3. clean and test the tape: more than 5 correctable errors, throw it out.

 For reading, 5 recoverable errors or any unrecoverable means:
  1. Clean the drive,
  2. Copy the data,
  3. If still have more than 5, clean and
     test the tape.  Any more than 5 correctable errors, throw
     it out.

 Many vendors will give replacements for tapes thrown out for
 the above reasons.  In particular the standards are much
 stricker for 3480 compatibles.

(The above is for 9trk, 6250 BPI and 3480.  The allowable error rates
 for 8mm and 4mm are much high (.1% skip and rewrite) and I don't
 have enough experience to say what the allowable limits are for
 end of life.)

Also, rewinding 9trk's every six months is said to be more likely
to cause errors, rather than prevent them.  I'd say copy data
you still want every 5 years, retire the tape after 10. 
(408) 765-4277; MS SC3-36, 3065 Bowers Ave, Santa Clara, CA 95052

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