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From: wietse@eurifb.UUCP (Wietse Venema)
Newsgroups: comp.unix.xenix
Subject: Was: Microport Unix V/AT and 9600 baud
Message-ID: <211@eurifb.UUCP>
Date: Fri, 25-Sep-87 17:56:36 EDT
Article-I.D.: eurifb.211
Posted: Fri Sep 25 17:56:36 1987
Date-Received: Sun, 27-Sep-87 09:33:31 EDT
References: <207@eurifb.UUCP> <105@suprt.UUCP>
Organization: EUR/Bedrijfskunde,PObox 1738,Rotterdam,Neth.
Lines: 35
Keywords: Microport 2.2 unreported bug
Summary: coming up

In article <105@suprt.UUCP>, jmsully@suprt.UUCP (John M. Sully         UUCP: ...!{sun | ucbvax | ihnp4}!amdcad!uport!techs) writes:
> In article <207@eurifb.UUCP>, wietse@eurifb.UUCP (Wietse Venema) writes:
> > [problem with large-buffer floppy writes/reads in a program that
> > spreads the input/output of tar across several floppies]
> 
> As of September 22, 1987 this bug had not been reported to us.  We have a 
> program which we use in-house which writes to the floppy in ~60K chunks
> and we do not have a problem with this.
>
> [remarks about raw devices and tar blocking factors]

(the original article appeared in comp.unix.wizards but this seems like
a more appropriate newsgroup)

In the following examples the kernel starts to print error messages when 
buffers of 10-20 kb are read/written from/to the raw 360kb floppy device:

	tar cvf - $* | while dd ibs=512 count=720 obs=20k of=/dev/rdsk/fd148
	do 
		(echo "\7next flop: \c"; read answer) >/dev/tty </dev/tty
	done

and:

	while dd ibs=20k count=18 obs=512 if=/dev/rdsk/fd148
	do 
		(echo "\7next flop: \c"; read answer) >/dev/tty </dev/tty
	done | tar tvf - $*

Results are not always the same; sometimes data remains unharmed, sometimes
tdd aborts due to an i/o error, and sometimes the kernel dies with a double
error.

	Wietse Venema		(uucp:		mcvax!eutwc1!wietse)
				(bitnet:	wswietse@heithe5)