problem accessing tape with tar on NT

Corinna Vinschen corinna-cygwin@cygwin.com
Mon Jan 27 16:38:00 GMT 2003


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@cygwin.com
Red Hat, Inc.

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