> > One problem that I have is that on the M76, with the Cipher drives
> > I can't get them to non-rewind on large files on NetBSD-1.5 Beta 1.
> > It will dd a boot loader, then at the end of a miniroot load, it senses
> > something and immediately autorewinds before starting the next file,
> > and then autorewinds after each file, making an improper boot tape.
> > It will tar on/off a tape just fine, though, so it is not hardware.
> > Ultrix handles it correctly, though.  I also noticed that the Ciphers
> > cause some sort of timeout or non request for next phase error on
> > the M76, but that does not seem to cause any problems.  And, when
> > I invoke a background erase ( mt erase & ) it locks up the console
> > until the erasing is done, rather than backgrounding the process.
> > It tries to background it, but never returns the console until done.
> > Is there anything offhand I could be doing wrong that might be
> > causing this to happen?
> 
> dd and tar access the device differently. Ive seen other NetBSD systems where
> tar works but dd doesn't, if i'm using the tape in non-rewind mode. I'm not
> sure exactly why it fails, (that was 1.4/alpha, btw, using a HP1533 dat) 
> though.. 

Does anyone else have any insights as to why my Ciphers might be going
into an autorewind mode after a dd to a non-rewind device:

   dd if=tapefile01 of=/dev/nrmt1h obs=512 conv=sync         (runs OK)
   dd if=tapefile02 of=/dev/nrmt1h obs=512 conv=sync         (runs OK)
   dd if=tapefile03 of=/dev/nrmt1h obs=10240 conv=sync       (autorewinds)
   dd if=tapefile04 of=/dev/nrmt1h obs=10240 conv=sync       (autorewinds)

The tape then has only tapefile04 on it, obviously.

Is it the tape driver not liking the obs=10240, or is it the driver
not liking a large file (tapefile03 and tapefile04 are rootdumps
and usr tars for example).  If tapefile02 is a larger file, sometimes
even it will kick the tape into autorewind.

Dd streams fairly well on an M76, but you can hear the blocks catching
up with the streaming every now and then.

Tar streams very well on an M76, with the tape never stopping until done
on any size file.

Is something like this a dd issue, or a driver issue, or what?

Ultrix works fine in both modes (dd and tar) to rewinding or non-rewinding
devices.  Is it time to go visit some old Ultrix source?  We don't have
to use it but we might learn some things from it.

I sense it might be a driver issue, possibly, but dunno for sure.

Any insights from the gurus et al., aboard, are appreciated.

Thanks

Bob