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Date:      Fri, 24 Nov 2000 01:10:09 +0000 (GMT)
From:      Terry Lambert <tlambert@primenet.com>
To:        fclift@verio.net (Fred Clift)
Cc:        opentrax@email.com, tlambert@primenet.com, stable@FreeBSD.ORG
Subject:   Re: Dedicated disks (was: Dangerously Dedicated)
Message-ID:  <200011240110.SAA05483@usr06.primenet.com>
In-Reply-To: <Pine.BSF.4.21.0011231005050.1914-100000@vespa.orem.iserver.com> from "Fred Clift" at Nov 23, 2000 10:24:28 AM

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> > > o	An increasing number of BIOS will divide by 0 when they
> > > 	are attempting to implement LBA addressing.  These
> > > 	systems simply _can not boot_, given FreeBSD's fake DOS
> > > 	partition table in its disklabel
> 
> again, 30 seconds in fdisk fixes this

This can be fixed, but hasn't been.


> > > o	The FreeBSD fake DOS partition table does not pass a
> > > 	number BIOS-based self-consistency checks (it needs to
> > > 	be fixed -- feel free to bell the cat), and so systems
> > > 	which use these checks in the BIOS to protect against
> > > 	boot sector virus infestation _can not boot_.
> 
> again, 30 seconds in fdisk fixes this

I don't agree with this one.  There is a checksum that is not
valid against the FreeBSD created partition tablem regardless
of what you do with FreeBSD fdisk.


> Several other things were mentioned that relate to dedicateds not playing
> well with other operating systems and utilities.  The response to all of
> these is  "Yes, but by definition, a 'dedicated' install is not required
> to interoperate with other systems since it is the only OS on the
> disk. (yes, multiple disks, a boot manager, etc but when I think
> dedicated, I dont think dual boot to two disks -- I think -- this is my
> FreeBSD web/file/print/etc server, and so why would I want to dual-boot? 

I have yet to see a reasonable justification as to why a DOS
partition table and MBR (or boot manager) causes any problems
that can't be overcome.

The only valid reasons I have seen put forth have come from
my own postings about historical hardware, and they all have
workarounds.

Let me add a third in the "pro" column (I'm 3 for 3 on being
the source of "pro" arguments, with this one):

o	If you have a disk which exceeds the allowable C/H/S
	values with its physical geometry, and neither the
	disk itself, nor the controller, fictionalizes the
	geometry, the DOS partition table can not describe
	the full disk in C/H/S terms, and some space will not
	be usable.

The refutation of this one is rather simple: the OS should use
the 32 bit sector offset and 32 bit sector count, instead of
the C/H/S values, if these two values are non-zero.  This is
described in numerous documents written about the DOS partition
table, and is even part of the PReP standard for PPC based
systems.

(I'm 3 for 3 on refuting them, too).


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.


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