reading dat tapes

Hi,
I've got a few tapes (2gb) made with retrospect, a software for apple systems.
I'd like to read all of them and put on a disk or a few dvds, thus I tried to
use my linux dat (20gb) with the command:
dd if=/dev/st0 of=/tmp/dat1 bs=1024
but it doesn't copy anything (exits with 0 bytes read and 0 write). Am I doing
something wrong or just Linux cannot read retrospect tapes (I guess it
should, being a raw copy)? Or simply I cannot read tapes of 2 gb with a 20gb
reader?
Any idea?

Thanks,
Luca
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Re: reading dat tapes

Luca Ferrari wrote:

> I've got a few tapes (2gb) made with retrospect, a software for apple systems.
> I'd like to read all of them and put on a disk or a few dvds, thus I tried to
> use my linux dat (20gb) with the command:
> dd if=/dev/st0 of=/tmp/dat1 bs=1024
> but it doesn't copy anything (exits with 0 bytes read and 0 write). Am I doing
> something wrong or just Linux cannot read retrospect tapes (I guess it
> should, being a raw copy)? Or simply I cannot read tapes of 2 gb with a 20gb
> reader?
> Any idea?

DAT tapes can use a variety of densities and block sizes, and can use
compression. You typically have to use "mt" to set the drive to use
the same settings as were used for writing the tape. A corollary of
this is that the drive used for reading the tape has to support the
format with which it was written.

--
Glynn Clements
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Re: reading dat tapes

At 18:01 19/09/2006, Glynn Clements wrote:


>Luca Ferrari wrote:
>
> > I've got a few tapes (2gb) made with retrospect, a software for
> apple systems.
> > I'd like to read all of them and put on a disk or a few dvds,
> thus I tried to
> > use my linux dat (20gb) with the command:
> > dd if=/dev/st0 of=/tmp/dat1 bs=1024
> > but it doesn't copy anything (exits with 0 bytes read and 0
> write). Am I doing
> > something wrong or just Linux cannot read retrospect tapes (I guess it
> > should, being a raw copy)? Or simply I cannot read tapes of 2 gb
> with a 20gb
> > reader?
> > Any idea?
>
>DAT tapes can use a variety of densities and block sizes, and can use
>compression. You typically have to use "mt" to set the drive to use
>the same settings as were used for writing the tape. A corollary of
>this is that the drive used for reading the tape has to support the
>format with which it was written.
>
>--
>Glynn Clements
>-


From experience with HP DAT drives there are issues with
compatibility across DDS versions.
HP have a tape storage compatibility matrix on their site somewhere.
I believe that a DDS1 is
not readable on a DDS4 for example, whereas a DDS2 is.

I have also seen tapes that can only be read on the original tape
drive manufacturers drive (hardware
compression differences perhaps) despite using the same operating
system/backup tool.

Regards
Carl


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