Hi 

My org uses SuSE 9 SLES servers and I used the following commands.

Turn off datacompression as Root run mt command that controls magnetic
tape
drive operation.

# Check datacompression status
myserver:~ # mt -f /dev/nst0 status

# Turns datacompression off 
myserver:~ # mt -f /dev/nst0 datcompression 0
Compression off.

I hope this helps if not someone on the list will guide you as I have
made a lot of progress thru this mailinf list.

Cheers


On Fri, 2005-09-30 at 14:10 +0200, uwe.kaufmann AT infoconsult DOT nu wrote:
> Hi Listers,
> 
> Just to give my 0.02EUR
> 
> > > mt -f /dev/nst0 defcompression off (or 0 depending on your mt)
> > > mt -f /dev/nst0 compression off (or 0 depending on your mt)
> 
> I am running SuSE 9.3 and the only available mt operation is
> "datcompression"
> 
> See:
> athene:~ # mt --version
> GNU mt version 2.5
> athene:~ # man mt
> [...]
>  datcompression
>               (some  SCSI-2  DAT  tapes) Inquire or set the compression
> status
>               (on/off). If the count is one the compression status is
> printed.
>               If  the  count is zero, compression is disabled. Otherwise,
> com-
>               pression is enabled. The command uses the SCSI ioctl to read
> and
>               write  the Data Compression Characteristics mode page (15).
> ONLY
>               ROOT CAN USE THIS COMMAND.
> 
> 
> And in fact I do have the problem that I use at one site the Tandberg SLR7
> without knowing how to switch off hw-compression. The mt datcompression
> {off|0} operation fails. That leads to my amanda.conf:
> 
> define tapetype SLR7 {
>     comment "just produced by tapetype prog (hardware compression on)"
>     length 16500 mbytes       # Manually decreased again
>     filemark 186 kbytes
>     speed 1300 kps
> }
> 
> athene:~ # dmesg | grep SLR
>   Vendor: TANDBERG  Model: SLR7              Rev: 0483
>   Type:   Sequential-Access                  ANSI SCSI revision: 02
> Attached scsi tape st0 at scsi0, channel 0, id 3, lun 0
> st0: try direct i/o: yes (alignment 512 B), max page reachable by HBA
> 1048575
> 
> 
> BTW: Is it true that a tape formerly written with hw-compression will
> "override" the 'drive compression off setting' because the compression
> on/off status has been written on the header of the tape? If yes, I should
> "reformat" a lot of tapes as described by Gene :-/
> 
> 
> Best regards
> Uwe
> 
> 
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-- 
Unix/ Linux Systems Administrator
Chuck Amadi
The Surgical Material Testing Laboratory (SMTL), 
Princess of Wales Hospital 
Coity Road 
Bridgend, 
United Kingdom, CF31 1RQ.
Email chuck.smtl.co.uk
Tel: +44 1656 752820 
Fax: +44 1656 752830