On Tuesday 10 December 2002 10:36, Richard B. Tilley ""(Brad) wrote:
>How does one remove compression from a quantum dlt 4000 tape drive
> that uses dlt 4 tapes?
>
>I have tried mt -f /dev/nst1 erase and then rewriting the amanda's
> tape label, but the drive always goes to 20GB compressed unless I
> do a density override and deselect the compression.
>
>My understanding is that these drives are to default to 20GB
>uncompressed and I would rather let amanda do the compression. As
> of now, I can set the density override each night when I load the
> tape, but I'd like the drive to default to this.
>
>The drives handbook talks about writing from BOT as a way to make
>changes to density, but it seems to me that using erase and then
>creating a new label would be from BOT.
You can probably to skip the erase. Particularly if its a whole
tape erase. No sense beating on the tape drives heads & drive
mechanism needlessly.
Here, I had a similar problem with DDS tapes and found that in
addition to setting the compression dipswitch on the drive to off,
I had do the compression override commands with mt while it was in
a rewound state, then write enough data from /dev/zero to force a
buffer flush in the drive, which then re-wrote the tape header
without the compression flag that keeps resetting itself everytime
you change the tape and it finds the compression flag set on the
freshly inserted tape.
Tape drives do a lot of housekeeping they don't always tell you
about in the lawyer written legaleze of the so-called instruction
manual. Am I a bit jaded? First, we kill all the lawyers. :)
You'll probably need to do this to all your tapes I'd expect. If
they are already labeled, save the label out to a scratch file with
dd, rewind it, do the compression off bits and the big write from
/dev/zero, rewind it and then use dd to restore the label. You'll
lose the data on that tape of course, but if you make a script out
of it that runs 15 minutes before amdump, and just let it take care
of things one tape at a time until all your tapes have been
'adjusted' you will be pretty safe. It won't be a disaster if it
runs too many tapes thru either.
--
Cheers, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz 512M
99.20% setiathome rank, not too shabby for a WV hillbilly
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