The drive doesn't have any dip switches - I even took the drive out of the
encosure and couldn't find anything.

I copied the wrong mt command over - 

Where I'm at now is looking at stinit ant the /etc/stinig.def file to create a
/dev/nst0l device which disables compression - I'm in the middle of another
test right now and can't try it out just yet - but if this works for me I'll
send it to the list.  We have a ton of these Sun SDLT 220 drives floating
around and want to use them.  


I ran some tests using hardware compression and wasn't impressed with the
results so I'm trying it with it off.




------ Original Message ------
Received: Thu, 29 Sep 2005 02:29:47 PM MDT
From: Gene Heskett <gene.heskett AT verizon DOT net>
To: amanda-users AT amanda DOT org
Subject: Re: Disable Tape Compression

> On Thursday 29 September 2005 12:08, Christopher Davis wrote:
> >I'm using Amanda on Fedora Core 4 with a Quantum SDLT 220 tape drive - I
> > want to disable hardware compression but I'm not sure of the best way
> > to do that.
> >
> >I can issue a command mt -f /dev/nst0 defcompression 1 which seems to
> > work (amtapetype doesn't give me the warning about hardware compresion)
> > but as I understand it this change goes away as soon as I change tapes.
> >  Meaning each time I insert a new tape I have to re-enter this command?
> >
> defcompression 1 turns it on, not off.  And there is probably a
> dipswitch of jumper setting someplace on the drive to turn it on
> permanently IF thats what you want.  Check your docs on the drive.
> 
> However, running hardware compression hides the tapes true size from
> amanda, so you have to make an educated guess in setting the
> tapetypes 'size'.  Amanda meas7ures the amount of data sent down the
> cable to the drive, and if amanda is doing the compression, which can
> handily beat the hardwares compression ratio in many cases, then
> amanda knows exactly how much the tape can hold.
> 
> So, generally speaking, we don't recommend hardware compression.  To
> give you an idea of how good the 'compress best' can be, I have a
> report of from of my recent runs that, with a 48 entry disklist, some
> compressed and some not, still put a bit over 17GB of real data in
> about 7.5GB of storage space used.   It won't do that every night of
> course, but often enough to pay for the cpu power it takes.
> >
> >How can I make the change permanent so that I don't have to worry about
> >manually changing a settting?
> >
> >
> >Any ideas or help would be much appreciated.
> >
> >
> >Chris
> 
> -- 
> Cheers, Gene
> "There are four boxes to be used in defense of liberty:
>  soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> 99.35% setiathome rank, not too shabby for a WV hillbilly
> Yahoo.com and AOL/TW attorneys please note, additions to the above
> message by Gene Heskett are:
> Copyright 2005 by Maurice Eugene Heskett, all rights reserved.
> 
>