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From: Robert Eckardt <roberte@mep.ruhr-uni-bochum.de>
Message-Id: <199609221238.OAA00975@ghost.mep.ruhr-uni-bochum.de>
Subject: Re: TANDBERG TDC3600 - need multiple 512
In-Reply-To: <199609220957.LAA11492@allegro.lemis.de> from Greg Lehey at "22. Sep. 96 11:57:13"
To: tito@agi.es
Date: Sun, 22 Sep 1996 14:38:40 +0200 (MET DST)
Cc: questions@FreeBSD.org
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> TITO writes:
> >
> >
> > I've a problem with make a tar backup to streamer TANDBERG.
> >
> >
> > When I use the option z ( to make tar with gzip ), the system returns this
> > bug.
> >
> > 	input/output error - must be multiple 512
> 
> Interesting one.  First, what it means: the driver wants a write
> length which is a multiple of 512 bytes.  That works well enough with
> tar normally, but not if you compress, in which case it writes in
> dribs and drabs.  You can fix it with:
> 
>    tar czf - <files> | dd obs=20b of=/dev/rst0
> 
> This will force a block size of 20 blocks.

Or you could use (from tar --help):
--block-compress        block the output of compression program for tapes

Therefore, 'tar -czf /dev/rst0 --block-compress <files>' works (for me)
(except that compression on my 486 stops the tape from streaming :-)

Robert