From: KPJ (kpj@sics.se)
Date: Sun May 09 1999 - 23:02:08 MDT
It appears as if Karsten Bänder <Karsten.Baender@ivm.de> wrote:
|
|> Most information on tapes is raw data, lists of names, numbers, etc.
|> Magnetic tapes, stored properly, do not crumble or otherwise degrade
|> easily. I am still using 9 track magnetic tapes that are older than I am
|> on a regular basis for list processing operations.
|
|Wrongo, BASF conducted a test which concluded, that even under ideal storage
|circumstances, 100% reliability is guaranteed only five years. Your 9-track
|magnetic tapes still work because they store a huge stream of analog data.
|Your ears have a built-in noise-reduction which screens out most of the bad
|audio data that comes in. But gradually, the quality of these recordings
|will fade. In adio recordings, the quality simply gets worse. In data tapes,
|it gets lost, because eventually, the errors destroy too many bits of data,
|making an error correction impossible. Much more with the high-packed data
|tapes of today.
Your analysis appears to match reality.
Any magnetic storage degrades with time _unless_ rewritten periodically,
e.g. every 5 years. A magnetic tape will eventually wear out by this,
but the data could be copied to a fresh tape each time, ad nauseam.
I copied my old 9 track magtape data to ExaByte technology some time ago,
but the tape transport unfortunately could no longer read some of the tapes
due to magnetic degradation. I understand there exist special methods
to read the data even after a normal tape transport will reject the tape,
but such methods cost much more to use, and unless the data loss would
mean a catastrophe, most would not consider those methods a viable solution.
_I_ sure did not.
My old Hollerith cards and paper tapes, however, show no degradation
whatsoever..
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