[sub.os.os9] Two processes writing to the same file in OS-9 68K

fdc@materna.uucp (Frank D. Cringle) (07/13/90)

We have been caused considerable grief recently by a problem which
appears to occur when two processes attempt to write to the same file
simultaneously.  This is not something we actually want to do, but it
can happen when two mis-coordinated folk start "make" in the same
directory at about the same time.  Two copies of the compiler run in
parallel, happily generating the same .r files etc.

The effect we see is a trashed hard disk -- garbage written over a large
section of the disk generally including some important directories. 
The multi-hour restore of about 100MB from a QIC Streamer is no fun!

I would like to find out if this effect is specific to our system, and
therefore probably due to some local hack, or if similar effects have
been observed elsewhere.

Here is the configuration:

* Eltec Eurocom-5 with OS9 v2.3
* Micropolis 1375 disk
* Miehle cacheing SCSI driver

Any tips greatly appreciated.  In the meantime I am going to hack make
so it opens a non-sharable lock file before proceeding.

Frank D. Cringle                | Tel. +49 231 5599 124
Dr. Materna GmbH                | fdc@materna.uucp
Vosskuhle 37
D-4600 Dortmund 1