On Saturday 16 November 2002 13:18, Marius Sorteberg wrote:
>Hi list,
>
>I use Amanda2.4.3 on FreeBSD 4.7, compiled from ports.
>My tapedevice is a DLT 15/30.
>
>I recently switched to software compression, and therefore whish
> to disable hardware compression. This is done with "mt comp off"
> on FreeBSD, and works well on my hardware. The tapedevice is
> external, in it's own case (the backup server is 1U).
>
>The "mt " command is lost after a reboot, or a powercycle on the
> tapedevice. A small script, run by cron would solve this, but is
> it "a better way"?
>
>I guess I'm looking for a setting in amanda.conf.
>
>Regards Marius Sorteberg
The most dependable way would be to raise the hood with manual in
hand so you can locate and set the dipswitch that most likely
controls that.
Bear in mind that some tape formats also store this setting on the
tape, and one must cause a flush to the media after doing this
without giving the drive a chance to re-read and reset this
variable. Doing the flush will cause it to re-write that hidden
header data with the compression turned off. This of course is on
a tape by tape basis, so one must treat all tapes in the cycle to
turn this off. Because that effectively wipes the tape, do it to
each in sequence immediately before amanda re-uses it. You may
have to write a short script to do this, and do it from crontab
about 15 minutes before amanda starts.
In your script, save the tape header block before doing this, and
restore it after (use dd) to keep amanda from upchucking because it
can't find the tape its expecting. It should look something like
this, using the non-rewinding device for /dev/tape:
-----------------
mt -f /dev/tape rewind
# save this tapes id header
dd if=/dev/tape of=scratch count=1
mt -f /dev/tape rewind
# one of thses should hit it
mt -f /dev/tape compression off
mt -f /dev/tape defcompression off
mt -f /dev/tape datcompression off
# now force huge write to flush buffers to tape
# don't use /dev/urandom, doesn't always work for this
dd if=/dev/zero of=/dev/tape bs=32k count=65535
mt -f /dev/tape rewind
# restore header for amanda
dd if=scratch of=dev/tape
mt -f /dev/tape rewind
---------------
Which should do it.
--
Cheers, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz 512M
99.19% setiathome rank, not too shabby for a WV hillbilly
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