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From: "Rodney W. Grimes" <rgrimes@GndRsh.aac.dev.com>
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Subject: Re: Mapped geometry vs. Actual
To: BRETT_GLASS@ccgate.infoworld.com
Date: Sun, 4 Aug 1996 09:39:36 -0700 (PDT)
Cc: msmith@atrad.adelaide.edu.au, randy@zyzzyva.com, hardware@FreeBSD.ORG
In-Reply-To: <9607048391.AA839174215@ccgate.infoworld.com> from "BRETT_GLASS@ccgate.infoworld.com" at "Aug 4, 96 09:39:26 am"
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> > FreeBSD's only interest in the disk geometry is to match whatever the
> > BIOS thinks, so that it can correctly locate the beginning of its
> > partition on the disk.  Finito.
> 
> Is this really true?
Yes.

> It seems as if it also tries to force disk slices to
> cylinder boundaries -- which is silly on ZBR drives or when sector mapping
> is done.

That is to maintain compatibility with other operating systems, if you don't
do this some other OS's fdisk may try to ``fix'' your MBR partition table
for you and make a royal mess of things instead.

Cylinder bondaries alignment must be retained if you ever let anything
bug FreeBSD /sbin/fdisk near your disk drive.

pfdisk will complain about off cylinder partition addresses, and if allowed
try to correct them.  Some of Microsoft's tools are not so nice, they'll
just fix them without telling you about it.

-- 
Rod Grimes                                      rgrimes@gndrsh.aac.dev.com
Accurate Automation Company                 Reliable computers for FreeBSD