On Friday 29 October 2004 23:23, Erik Anderson wrote:
>Hello - I have a Quantum DLT7000 drive, and I'm wondering how I go
>about disabling hardware compression on it. I did some searching,
> and it seems that I should be able to issue this command:
>
>lpdlnx00 LPD # mt -f /dev/nst0 compression 0
>/dev/nst0: Input/output error
>
>I am certain that /dev/nst0 is the correct device node for the
> drive:
>
>lpdlnx00 LPD # mt -f /dev/nst0 status
>SCSI 2 tape drive:
>File number=-1, block number=-1, partition=0.
>Tape block size 0 bytes. Density code 0x0 (default).
>Soft error count since last status=0
>General status bits on (50000):
> DR_OPEN IM_REP_EN
>
>I'm trying to get this disabled so I can get an accurate reading
> from amtapetype.
>
>Thanks!
>-Erik Anderson
Hi Erik;
I'm not familiar with the DLT drives, but generally speaking, there
should be a dip switch or flea clip programmable setting someplace on
the drive to set that on or off. Dig out the drives manual if you
can, or pester your vendor for it if you didn't get it.
Please be aware that most drives will set themselves according to the
data in a hidden header on the leader of the tape, doing this as they
go thru the tape recognition phase when a tape is inserted in the
drive.
To defeat that, and make an uncompressed tape out of a tape that has
been written with the compression on, will require that the correct
software command be issued (in my case it wasn't a 0, but an 'off'
command issued by mt), and then sufficient data written to force the
drive to flush its buffers, at which point the compression flag on
the tape will be reset. This is commonly 4 to 10 megs of garbage to
force this. I had written a script that would rewind the tape, read
out the tape label to a scratch file with dd, rewind it again, issue
those compression off commands, then rewrite the label block just
read with dd, followed by another 5 megs worth of "dd if=/dev/zero
bs=32768 count=160 of=/dev/nst0", and then rewind the tape again.
I had to do it wholesale to a stack of DDS2's about 2 feet high,
hence the short bash script.
I hope this is usefull.
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
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by Gene Heskett are:
Copyright 2004 by Maurice Eugene Heskett, all rights reserved.
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