Subject: Re: Tapeboot problem SOLUTION
To: None <port-sun3@NetBSD.ORG>
From: der Mouse <mouse@Collatz.McRCIM.McGill.EDU>
List: port-sun3
Date: 12/12/1995 14:32:51
> In most older UNIX tape systems that I've seen, if you use the
> character special device, you can write a record of any size within
> the minima and maxima of the medium ([...]).  With 9-track tapes, the
> range was pretty wide (1 byte to 10's of K).

Yeah, that's the traditional tape model.  QIC tapes break it rather
badly.  I've seen the equivalent of the following with QIC tapes:

	% dd if=/dev/zero bs=512 count=20 of=/dev/qic-tape
	20+0 records in
	20+0 records out
	% mt -f /dev/qic-tape rew
	% dd if=/dev/qic-tape of=/dev/null bs=10240
	1+0 records in
	1+0 records out

The traditional model would have produced "0+20 records in".
Similarly, I've also seen the converse, writing large records and
reading small records.  QIC tapes seem to behave as if they are streams
of 512-byte units, rather than streams of more-or-less-arbitrary-size
records.  (Plus tape marks, of course.)  Certainly SunOS behaves this
way; I just tried it.

Very annoying. :-(

					der Mouse