> > > something like this:
> > > 
> > > tar -c -v -f - -T /var/run/tapefilelist |
> > >   ssh -c blowfish sysfoo buffer -m 4m -p 25 -B -o /dev/rst1 -t
> > > 
> > > This works, but is very slow and I can only fit about 3.2 GB on a 4 GB tape.
> > > CPU load on both machines is less than 5% and net usage is about 500 K/s.
> > 
> > ssh uses lots of cpu for scrambling
> 
> Yes, but if CPU load is under 5% (95% idle), it doesn't explain the slow
> speed.  I guess the DAT drive writes some data, then stops, rewinds the
> tape, writes some more data etc.  But why?  I have a 4 MB buffer which should
> be enough to keep the tape streaming, IMHO..

what blocks does "buffer" program use?

try setting blocks to 0 (mt setblk 0) and set 32kB output block size in
"buffer". i do not use buffer no i don't know what's the options