> > > with -B.
> > > And no, I don't think it's a good idea using the drive's compression
> > > mechanism for _backups_...
> > 
> > why?!
> 
> Partly because the program cannot tell in advance how much is going to
> fit onto one tape and to prompt you to change tapes _before_ the end
> of the tape is reached. "dump" is not suited for dealing with multiple
> tapes with different capacities.

from man dump:

     dduummpp examines files on a filesystem and determines which files need to be
     backed up.  These files are copied to the given disk, tape or other stor-
     age medium for safe keeping (see the --ff option below for doing remote
     backups).  A dump that is larger than the output medium is broken into
     multiple volumes.  On most media the size is determined by writing until
     an end-of-media indication is returned.  On media that cannot reliably
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     return an end-of-media indication (such as some cartridge tape drives)
     each volume is of a fixed size; the actual size is determined by the tape


so how to turn this writing until eom on?!