For some reason I keep thinking they are 20GB tapes. Thanks for the 
clarification.

On Monday 02 June 2003 14:08, donald.ritchey AT exeloncorp DOT com wrote:
> DLT 8000 drives are 40 GB native, 80 GB Compressed.
>
> We use them here.
>
> Donald L. (Don) Ritchey
> E-mail:  Donald.Ritchey AT exeloncorp DOT com
>
>
> -----Original Message-----
> From: Brendon Colby [mailto:bren AT midco DOT net]
> Sent: Monday, June 02, 2003 2:03 PM
> To: amanda-users AT amanda DOT org
> Subject: Re: Few questions.
>
> On Monday 02 June 2003 10:40, Gene Heskett wrote:
> > If you then had to recover, you would need only the last 'dumpcycle'
> > tapes.  Note that I didn't say 7 though, because you might be running
> > a 5 day a week runspercycle, so that would be only the last 5 tapes.
>
> Ok. Thanks - this just clicked for me.
>
> > One would use the capacity the makers says it has when the compression
> > is turned off.  Software is the prefered method, for 2 reasons.
>
> My tapes say 40* - 80* GB (* = compressed). This is a DLT 8000 drive. This
> means that I have a 20GB capacity uncompressed? (Just to clarify.)  The 40
> -
>
> 80 GB means I can get between 2 to 4 times the storage with compression on?
>
> > 1. gzip can normally outcompress the hardware compressors in most
> > drives.  Night before last, the disklist and dumpcycle positioning
> > was such that I put something over 10 gigs on a 4 gig DDS2 tape. Of
> > course I don't do that every nite :)
> >
> > 2. amanda counts bytes sent to the tape.  If the hardware compression
> > is on, then amanda has no clear view of the tapes capacity and will
> > happily write till it hits EOT if you are feeding it already
> > compressed files, like a whole dir full of rpm's or tar.bz2's, which
> > will probably grow some in the compressor.  So you have to set the
> > tapetype to something less than the makers propaganda claims & then
> > (optionally, I've not been able to prove its effective) sacrifice a
> > chicken.  If its turned off, then amanda has a pretty good view of
> > what the tape can hold and will fill it reliably to 95+% without ever
> > hitting the tapes EOT.
> >
> > There is an amtapetype utility in the distribution that can test that
> > for you.  But start it early in the day, it takes a while to run.
>
> I have already decided to use software compression (esp. for reason #2
> above).
> I will have to compile the distro from the Amanda site as the Debian
> packages
> must not contain the amtapetype utility.
>
> Thanks for everyone's help.

-- 
Brendon Colby
Systems Administrator
Midcontinent Communications