Thanks to everyone for your replies.

Ok, so what I really wanted to do was to use software compression, and not
hardware compression.

Cyrille's suggestion sounds like what I need, but again I'm not sure whether
using this command will mean that compression is turned off "permanently". 
I'll look into the stinit command in the meantime...

Now I'm wondering about the tapes I've already used while hardware
compression was still on.  Obviously the tape drive will need to feed those
tapes through its decompression mechanism to read them again.  If I use the
command as suggested by Cyrille, will that mean that the used tapes become
unreadable, or that you have to manually turn compression on and off (I've
read the the compression command overrides the defcompression one for the
currently loaded tape)?

Thanks.

Joe


Cyrille Bollu wrote:
> 
> owner-amanda-users AT amanda DOT org a ?crit sur 04/07/2006 13:17:46 :
> 
>> 
>> Dear all,
>> 
>> I just want to clarify something about compression:
>> 
>> My understanding is that you can use either software or hardware
>> compression, or can switch between the two if needed.
>> 
>> What is generally, in your experience, the best of the two to use?
>> 
>> To switch off hardware compression, I believe I should use:
>> mt -f /dev/nst0 compression 0 
>> 
>> Does this command switch it off permanently until you use the 
> following?:
>> mt -f /dev/nst0 compression 1
>> 
>> or will hardware compression switch back on, say, after a reboot?
> 
> AFAIK, there's another option.
> 
> from "mt" man pages:
> 
>   defcompression
>               (SCSI tapes) Set the default compression  state.  The  value 
>  -1
>               disables  the  default compression. The compression state 
> set by
>               compression overrides the default until a new tape is 
> inserted.
>               Allowed only for the superuser.
> 
> so one should use:
> 
> mt -f /dev/nst0 defcompression 0 
> 
> Cyrille
> 

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