[372] in linux-scsi channel archive
Re: Reading Exabyte tapes from Sun et al
daemon@ATHENA.MIT.EDU (Andreas Koppenhoefer)
Fri Jul 14 19:44:46 1995
From: Andreas Koppenhoefer <koppenas@koppenas.informatik.uni-stuttgart.de>
To: scldad@sdc.com.au (Stephen Davies)
Date: Fri, 14 Jul 1995 18:44:16 +0200 (MET DST)
Cc: linux-scsi@vger.rutgers.edu
In-Reply-To: <199507141011.TAA18882@mustang.sdc.com.au> from "Stephen Davies" at Jul 14, 95 07:41:52 pm
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> From: "Stephen Davies" <scldad@sdc.com.au>
> Subject: Reading Exabyte tapes from Sun et al
> To: linux-scsi@vger.rutgers.edu
> Date: Fri, 14 Jul 95 19:41:52 +0930
> Sender: owner-linux-scsi@vger.rutgers.edu
>
> I can happily write to my Exabyte drive and read back from tapes created
> on my machine but I cannot read tapes from other machines such as Sun/OS
> boxes.
>
> I have tried setting the tape blocksize to 0 as per the FAQ but still get
>
> 19:34:35> dd if=/dev/rst0 |pg
> dd: /dev/rst0: I/O error
> 0+0 records in
> 0+0 records out
>
> and
>
> tar: read error on /dev/rst0 : I/O error
>
> These mesage appears with or without a "mt setblk 0" and with all of the
> bs settings that I have tried so far.
>
> Could sombody please tell me the magic words.
Maybe the magic is: Add 'bs=<bufsize>' argument to dd command. bufsize
should be large enough so that the largest block on tape can
fit. SunOS/Solaris writes tapes with block of variable size. Linux
applications must use read buffer sizes large enough.
Example: if you write on SunOS/Solaris with tar but without '-b busize'
argument, then tar defaults to writing blocks of 10k byte in size. A
dd command with bs=10k should work for linux in this case.
If you don't specify bs=.., dd will work with size of 512 byte which
is far too small, since Exabytes natural block size is about 1k.
If the size of blocks is unkown, then use bs=64k. That shouln't
hurt. Exabyte tape drives use block of up to 64k in length. Blocks
longer than that are broken down to smaller pieces by SunOS/Solaris
tape driver.
If this doesn't help, then check Exabyte drive capabilities: tapes
written to drives with compression capability cannot be read on drives
without. Older Exabyte 8200 drives cannot read tapes with capacity of
more than 2.3 Gbyte.
Hope this helps,
Andreas
- --
Andreas Koppenhoefer, Student der Universitaet Stuttgart, BR Deutschland
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