Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!husc6!necntc!dandelion!ulowell!page
From: page@ulowell.cs.ulowell.edu (Bob Page)
Newsgroups: comp.sys.amiga
Subject: Re: The secrets of the file system (was FillDisk)
Message-ID: <2085@ulowell.cs.ulowell.edu>
Date: Wed, 2-Dec-87 14:07:40 EST
Article-I.D.: ulowell.2085
Posted: Wed Dec  2 14:07:40 1987
Date-Received: Sun, 6-Dec-87 07:41:52 EST
References: <6098@jade.BERKELEY.EDU> <2080@ulowell.cs.ulowell.edu>
Reply-To: page@swan.ulowell.edu (Bob Page)
Organization: University of Lowell, Computer Science Dept.
Lines: 34

I wrote in 2080@ulowell.cs.ulowell.edu:
>You can force a disk validation by running DiskChange DH0:

Arrgh!  DON'T DO THIS unless the people who supply your
harddisk.device (or whatever your driver is called) says it's OK!

I realized DiskChange makes some NON-STANDARD calls to the driver.
When I say non-standard, I mean IORequests that are not part of the
basic and required functions for a device, like open, close, read,
write, etc.  Each device can have its own non-standard functions
for special commands unique to that device.

DiskChange ASSUMES it is talking to a 5-1/4 inch disk device, which
happens to have the same non-standard commands as trackdisk.device.

It may be that your driver writer also implemented the trackdisk's
non-standard commands, but you DON'T KNOW what might happen when
DiskChange says "MOTOR OFF" to your harddisk ... it might mean
"FORMAT" to the driver!

So DON'T use DiskChange DHn: unless you are sure it's OK.  It's OK for
CLtd drives (they tell you about DiskChange in their documentation), I
suspect it is OK for everybody else's drive too, but make sure before
you do it.

If you are hanging on to my last article about disk validation, make
sure you hang on to this one too.  Sorry I didn't realize the danger
before I posted the article.

..Bob
-- 
Bob Page, U of Lowell CS Dept.  page@ulowell.edu  ulowell!page
"I've never liked reality all that much, but I haven't found a
better solution."		--Dave Haynie, Commonkeave to a