Manipulation DAT tapes on linux

[Ilya Palagin]

40GB is a "marketing" volume.  Of course, 20GB is "marketing" bytes. The real
size is about 19GB.  DDS tape drives use hardware compression, you don't need
to enable it.  Storing jpegs or avi's, you'll get your 19GB.  Compression for
text files will be more sensitive.  Average is about 25-28GB per tape.

Quoting JM <jerome-mhXWc29+iYPyG1zEObXtfA at public.gmane.org>:

> thanks for all your replies..
>
> hmm.. the tape says? 20G for uncompressed and 40G for compressed...
>
> does this mean doing tar -zcf /dev/st0 is the 40G?
> or
> i have to activate the compression and let the drive its job?
>
>
> TIA
>
> On Wednesday 17 November 2004 13:30, Ilya Palagin wrote:
> > JM wrote:
> > > Hi,
> > >
> > > 	I have a 4mm DDS-150 tape in linux and I was wondering if someone can
> > > answer this questions.
> >
> > First - you need 'mt' tools installed.
> >
> > > 	is it possible to extract selected file or files from an archive without
> > > extracting all the data from the tape?
> >
> > Extract separate files like this:
> >
> > tar xvf /dev/st0 /home/user/file01
> >
> > > 	is it possible to add a directory with files to a tape archive? (tape
> > > has an existing data on it)
> >
> > Jump to the end of data:
> > mt -f /dev/nst0 eod
> >
> > And add directory
> > tar cvf /dev/nst0 /home/dir
> >
> > > 	is it possible to get the tape usage?
> >
> > Rewind to the end of data and get current block, see man mt.  Then
> > calculate taken space.
> >
> > > 	what i usually do is tar -cvf /dev/st0 ..... .... ....
> >
> > Use /dev/nst0 for multiple archives, this device doesn't rewind tape
> > after command execution.  For instance, you have 5 archives on a tape.
> > To extract file /etc/passwd from archive #3, execute:
> >
> > mt -f /dev/nst0 fsf 3
> > tar xvf /dev/nst0 /etc/passwd
> > mt -f /dev/nst0 rewind
> >
> > > TIA,
> > >
> > >
> > > --
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>




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