>For a good tapesystem we also need basic volume handling and 
>label-processing.

FYI the following paper from the LISA VI conference (Oct 92)

>           DeeJay, the Dump Jockey and Daemon of the Jukebox
>                 A Heterogeneous Network Backup System
> 
>                             by Howie Kaye
>                            and Melissa Metz

Describes a backup system implemented using infinite length virtual 
tape volumes using ANSI tape labels and an relational database (early
ingres) to keep track of which tapes hold which volumes etc.

Anyway, it sounded like you didn't have to do much at the device level
to achieve this.  

I had originally planned to port the thing to work with postgres, but 
never spent much time on it.

--sjg