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Re: hardware vs software compression (was Re: amflush/amcheck not in sync?)
2003-04-24 06:47:04
Hi
sounds like complete 'hogwash' to me. IF you can recover a hardware
compressed file you can restore a software compressed file. From my
experience if the tape's damaged then that's it, unless you pay someone
with specialist capabilities to get the data off. You may have some luck
with being able to get past the bad sections with manual intervention
(dd and the like), but in most modern drives the error correction
algorithms are such that if it sees a bad write it will inform you. I
guess there's other things like water/fire damage, but then you're back
in the hands of data recovery specialists anyhow so....
This being why it's recommended to only give tapes a limited life span
and then archive or destroy them.
I guess what they mean is thet the recovery specialist won't know if
they've got good data or not..but if you supply then with the
compression programs used it shouldn't be a problem.
Personnally I'll stick with software compression.
--
Martin Hepworth
Senior Systems Administrator
Solid State Logic Ltd
+44 (0)1865 842300
Jeroen Heijungs wrote:
At 12:23 23-04-03 -0400, Gene wrote:
>To allow amanda to have a good view of the tape, and because gzip
>can compress better than the hardware, sometimes by large amounts,
>its generally recommended the drives compressor be shut off
>permanently by this group. It less amanda hassle in the long view.
It was recommended to me to NOT use software compression, with
the following reason:
"If a software compressed file is damaged, the complete file/tape is
not readable anymore and therefore useless. If it is NOT compressed
the rest of the tape/file may be readable, and therefore probably
restorable."
I have never had the opportunity to test this, does anyone has some
thoughts and/or comments on this?
I now use the hardware compression, and not the software compression,
the tapes are big enough, so there is no real problem for the time being.
tia
Jeroen Heijungs
het Muziektheater
Amsterdam, The Netherlands
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