Subject: Re: Configuring a SEAGATE DAT tape drive
To: Dave Archer <>
From: Yoseff Francus <>
List: port-pmax
Date: 03/21/2000 16:56:27

That makes sense. 

However, I was getting far far less than 2GB on a when using dump to create
the tape.
What is even odder is that while dump does not work very well I was
able to tar a 1.7GB filesystem to the tape without a problem and without
the message that only one density is supported. I wonder why dump and tar
give different behaviors.


Date:    Tue, 21 Mar 2000 16:50:52 EST
To:      Yoseff Francus <>
From:    Dave Archer <>
Subject: Re: Configuring a SEAGATE DAT tape drive

DAT drives use hardware compression and thus don't have a fixed density
in terms of the bits sent from the computer since this depends on the
compression rate.  The drive you have is a DDS-1 drive which physically
holds 2GB on a 90m tape, so you can do the math to work out what the
uncompressed density is.  Typically they're advertised as 4GB with the
assumption of 2:1 compression, but if the files you're backing up are
mostly already compressed, you'll get closer to 2GB.  


Yoseff Francus wrote:
> Looking at the tz.c code it looks like only one density is supported
> for PYTHON tape drives. WHat is the denisty that is supported?
> yf
> Date:    Tue, 21 Mar 2000 14:43:07 EST
> To:
> From:    Yoseff Francus <>
> Subject: Configuring a SEAGATE DAT tape drive
> I have a Seagate STD64000N-SB external 4GB DAT drive. When I attempt
> backups I am not getting anywhere near that. I have a feeling that
> I need to somehow configure different densities for it but have no idea
> where to even begin. Is anyone using this model (Scorpion family)?
> I am running 1.4.1 on a DECstation 5000/120 (3MIN).
> yf