> I always make an image when burning from different parts of disk, my
> problem is burning dvd's while doing other disk I/O - with growisofs
> this results immediately in more and more buffer underruns. I need some
> fifo such like cdrecord has.

Some jobs have real time constraints.  Audio and video spring to mind
as household examples, but there are other areas, like process control.

Some jobs that don't have hard real time requirements would benefit
from an I/O version of nice.  These days it is often the I/O, rather
than CPU cycles, that is the scarce resource.