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From: Mike Meyer <mwm@mired.org>
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Date: Tue, 5 Jun 2001 18:14:20 -0500
To: Nathan <list@khmere.com>
Cc: questions@freebsd.org
Subject: Re: documentation help, installation and the swap partition
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Nathan <list@khmere.com> types:
> I am trying to document how the partitions are laid out in FreeBSD and I
> have noticed that the installation will place the sector offsets of the
> b (swap) partition before the last partition. And will also place the
> sector offsets of the largest partition as the last regardless to its
> name (ie: d or h)
> 
> The question is why ? is it due to performance reasons ? or safety ? or
> other ? I have looked for specific documentation on this but I can't
> seem to find it.

Both your assertions are false - see label below. Then again, one of
your assumptions is false. FreeBSD doesn't lay out partitions; users
do. There are two tools for doing that: disklabel and
sysinstall. Sysinstall may default to the behaviors you mention;
disklabel doesn't.

Come to think of it, the default behavior for sysinstall is to
allocate standard-size partitions for the initial partitions, and dump
everything else into the last one. Given that modern disks are *much*
larger than those standard-size partitions, that will tend to make the
last partition the largest one on the disk.

#        size   offset    fstype   [fsize bsize bps/cpg]
  a:  5120000        0    4.2BSD        0     0     0   # (Cyl.    0 - 5417*)
  b:  1048576  5120000      swap                        # (Cyl. 5417*- 6527*)
  c: 14666337        0    unused        0     0         # (Cyl.    0 - 15519*)
  e:  5120000  6168576    4.2BSD     1024  8192    16   # (Cyl. 6527*- 11945*)
  f:  3377761 11288576    4.2BSD     1024  8192    16   # (Cyl. 11945*- 15519*)

	<mike
--
Mike Meyer <mwm@mired.org>			http://www.mired.org/home/mwm/
Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.

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