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Date:      Fri, 24 Jul 2009 22:09:00 -0600
From:      Scott Long <scottl@samsco.org>
To:        "M. Warner Losh" <imp@bsdimp.com>
Cc:        svn-src-head@freebsd.org, mav@freebsd.org, src-committers@freebsd.org, svn-src-all@freebsd.org, cperciva@freebsd.org
Subject:   Re: svn commit: r195817 - head/usr.sbin/sysinstall
Message-ID:  <4A6A855C.7090003@samsco.org>
In-Reply-To: <20090724.235420.319856209.imp@bsdimp.com>
References:  <4A68DA56.60301@samsco.org>	<20090724.233458.1683324074.imp@bsdimp.com>	<4A6A7F2D.90807@samsco.org> <20090724.235420.319856209.imp@bsdimp.com>

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M. Warner Losh wrote:
> In message: <4A6A7F2D.90807@samsco.org>
>             Scott Long <scottl@samsco.org> writes:
> : M. Warner Losh wrote:
> : > In message: <4A68DA56.60301@samsco.org>
> : >             Scott Long <scottl@samsco.org> writes:
> : > : M. Warner Losh wrote:
> : > : > In message: <4A66D0F4.4030108@FreeBSD.org>
> : > : >             Alexander Motin <mav@FreeBSD.org> writes:
> : > : > : Colin Percival wrote:
> : > : > : > Author: cperciva
> : > : > : > Date: Wed Jul 22 03:50:54 2009
> : > : > : > New Revision: 195817
> : > : > : > URL: http://svn.freebsd.org/changeset/base/195817
> : > : > : > 
> : > : > : > Log:
> : > : > : >   Remove the "dedicated disk mode" partitioning option from sysinstall, in
> : > : > : >   both the disk partitioning screen (the 'F' key) and via install.cfg (the
> : > : > : >   VAR_DEDICATED_DISK option).  This functionality is currently broken in 8.x
> : > : > : >   due to libdisk and geom generating different partition names; this commit
> : > : > : >   merely acts to help steer users away from the breakage.
> : > : > : >   
> : > : > : >   Submitted by:	randi
> : > : > : >   Approved by:	re (kensmith)
> : > : > : > 
> : > : > : > Modified:
> : > : > : >   head/usr.sbin/sysinstall/disks.c
> : > : > : 
> : > : > : Is there any other way to not align FS block to the ugly legacy 63
> : > : > : sectors per track boundary with sysinstall now? I think RAIDs won't be
> : > : > : happy. May be it would be better to fix it?
> : > : > 
> : > : > The reason we do it like this is because the boot blocks occupy the
> : > : > first cylinder group.  Which with today's fake goemetry is 63
> : > : > blocks...
> : > : > 
> : > : 
> : > : I already covered this.  Unfortunately, Randi didn't take my bait. 
> : > : Anyways, '63' is a minimum, it's not a singular value.  It's also
> : > : an incredibly bad default.
> : > 
> : > Yes.  256 is just as good as 63, unless the geometry reports more than
> : > 256 heads, which I don't think is possible...
> : > 
> : > Warner
> : 
> : If there is a BIOS in existence that can't find sector 256, then it 
> : likely can't boot off of anything other than partition 1 in the fdisk
> : table.  I bet that bugs like that were likely caught 15-20 years ago.
> 
> I think you were missing the point I was trying to make, I must have
> been unclear.
> 
> If there were more than 256 sectors in the first cylinder, then
> starting at 256 would overlap.  This is largely a theoretical
> problem, I think, since I don't think that the BIOS can report a
> geometry > 64.
> 
> The only issue that I can think of is that FreeBSD's fdisk wants to
> have things on cylinder boundaries, which 256 isn't, so fdisk will
> bitch and moan...
> 
> Warner

Ah, we will never be freed of the CHS bonds, will we.  Oh well.

Scott




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