An irritating problem.

["James K. McConnell" <jkm tbred com>]

Hello;

I've just installed a Sony SDT-7200/BMI DAT on my RH 6.1 system.
Installation was a snap, just pop it on the SCSI bus, and everything
seemed fine.  The drive is a 4/8GB DAT, meaning it supports a 
capacity of 4GB in native mode, and 8GB in compressed mode.  However
whenever I tar/dump/cpio to the drive, it cuts off after 4GB of data.

This is a problem, since I have a 9.1GB disk, with 8GB partitioned, 
and I need to backup around 6GB.  I get these results trying to change
the compression settings:

[root zeus /root]# mt -f /dev/st0 status
SCSI 2 tape drive:
File number=1, block number=64, partition=0.
Tape block size 512 bytes. Density code 0x13 (DDS (61000 bpi)).
Soft error count since last status=0
General status bits on (1010000):
 ONLINE IM_REP_EN

[root zeus /root]# mt -f /dev/st0 datcompression
Compression off.

[root zeus /root]# mt -f /dev/st0 datcompression on
/dev/st0: Drive does not support compression.

[root zeus /root]# mt -f /dev/st0 compression 1
/dev/st0: Input/output error

[root zeus /root]# mt -f /dev/st0 compression 2
/dev/st0: Input/output error

[root zeus /root]# mt -f /dev/st0 densities
Some SCSI tape density codes:
code   explanation
<snipped out a bunch>
0x00   default
0x13   DDS (61000 bpi)
0x24   DDS-2
0x25   DDS-3

[root zeus /root]# mt -f /dev/st0 setdensity 24
/dev/st0: Input/output error

[root zeus /root]# mt -f /dev/st0 setdensity 0x24
/dev/st0: Input/output error

[root zeus /root]# mt -f /dev/st0 defcompression 1
[root zeus /root]# mt -f /dev/st0 datcompression
Compression off.

I'm using an 8GB DDS-2 120m tape.

So, I'm at a bit of a loss.  I've been through all the docs I
can find on Sony's website/faxback system.  I found that there
is a DC (presumably "disable compression") jumper on the drive.
It isn't jumper'd.  What am I missing here?  Do I need to give
the st module additional parameters at boot time?  Shouldn't
this just work?  I have 2 other systems that are about to be
put into service where this will also be a problem, and one
system with a SDT-9000 (12/24GB) that will pass the 12GB mark
in days, and I presume the compression won't work for any of
these either.

Anyway, I can provide more info if required.  I can't shake the
feeling that I've missed something obvious here; hopefully
someone will point it out.

Jim