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 <[email protected]>
>-


 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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