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From: minow@mountn.dec.com (Martin Minow)
Newsgroups: comp.sys.mac.programmer
Subject: Re: SCSI Help
Message-ID: <1908@mountn.dec.com>
Date: 12 Sep 90 14:24:51 GMT
References: <917@beguine.UUCP> <9927@goofy.Apple.COM>
Reply-To: minow@bolt.enet.dec.com (Martin Minow)
Organization: Digital Equipment Corporation
Lines: 25

In article <9927@goofy.Apple.COM> stevec@Apple.COM (Steve Christensen) writes:
>If all you want to do is write all zeroes to all blocks on the disk, then
>just make write requests to the driver.

Sorry, but this doesn't write to "hidden" blocks, such as the partition
maps, blocks outside the partition,  and the blocks containing the driver
itself.  Also, there may be blocks on the disk that are not addressable by
the driver (that the disk uses for bad block replacement).

While you can write direct calls to the scsi driver without much
difficulty (you'll need the disk specification and/or the Ansi SCSI-II
draft specification), you may still have problems if, for example, you
need to handle errors.  Also, if you are trying to prevent all forms
of "covert channel" attacks, you will also have to reset all drive
control parameters (mode selects).

If all you want to do is erase the disk, use the "HD Setup" program
to reformat it, and DiskExpress to write zeros.

There are several products, such as Ft Knox that erase disks to
U.S. DoD standards.  I would recommend using one of these, rather
than trying to write your own.

Martin Minow
minow@bolt.enet.dec.com