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Date: Mon, 27 Jan 2003 15:17:02 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: Gnuwin <cygwin AT cygwin DOT com>
Subject: Re: problem accessing tape with tar on NT
Message-ID: <20030127141702.GU2117@cygbert.vinschen.de>
Reply-To: cygwin AT cygwin DOT com
Mail-Followup-To: Gnuwin <cygwin AT cygwin DOT com>
References: <NBBBKKHEOHOEPNCALMIGIEECDJAA DOT kris DOT thielemans AT ic DOT ac DOT uk> <NEBBKLAEEMDJBCGCCAOGCEHECJAA DOT kris DOT thielemans AT ic DOT ac DOT uk>
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In-Reply-To: <NEBBKLAEEMDJBCGCCAOGCEHECJAA.kris.thielemans@ic.ac.uk>
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On Mon, Jan 27, 2003 at 02:09:50PM -0000, Kris Thielemans wrote:
> (The tapes were generated with block size 20. Does that happen to be the
> default?).

Once the typical blocksize was 5120 bytes on tapes.  Today it's varying
but many drive types support different block sizes.

>      - This version supports setting blocksize to 0 to enable the variable
>        blocksize feature since Cygwin V1.1.3.
> ----------
> No clue what this means.

With fixed blocksize (e. g. mt setblk 512), the NT tape driver reads
and writes only blocks with the set blocksize (512 bytes in the above
example).  With variable blocksize (mt setblk 0), the NT tape driver
reads any block, regardless of it's size on tape and writes a block
with the size given to write(), this way potentially writing each block
with another size (as far as the driver allows, see `mt status 2',
"min block size" and "max block size").

Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Developer                                mailto:cygwin AT cygwin DOT com
Red Hat, Inc.

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