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Date:      Wed, 8 Jan 2003 21:22:52 -0600
From:      Mike Meyer <mwm-dated-1042514573.88afbd@mired.org>
To:        JacobRhoden <jrhoden@unimelb.edu.au>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: web write-up
Message-ID:  <15900.60172.518135.406735@guru.mired.org>
In-Reply-To: <200301091255.39730.jrhoden@unimelb.edu.au>
References:  <98130130380.20030108095305@telus.net> <3E1CCBDD.9090209@crystal.com.au> <200301091255.39730.jrhoden@unimelb.edu.au>

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In <200301091255.39730.jrhoden@unimelb.edu.au>, JacobRhoden <jrhoden@unimelb.edu.au> typed:
> On Thursday 09 January 2003 12:09, Shaun Dwyer wrote:
> > is they probably didn't make seperate slices for /, /var and /usr.
> 
> What difference does it make as to wether these partions are seperate. I 
> realise if you have more than one ide drive then having them on seperate 
> drives is alot better. On single drive machines I usually make only one 
> partion, what reasons are there to slice it?

[SWAG follows]

>From a performance standpoint, putting them on separate slices on the
same disk is probably a loss. It forces the blocks in those file
systems to live spread out across the disk, meaning the time
optimizations are constrained to those blocks, whereas if you put them
all in one file system then the disk scheduler can play with the
entire disk.

That said *THIS DOESN'T MAKE ANY PRACTICAL DIFFERENCE*. The scheduler
already slices partitions up into cylinder groups and tries to make
files live on specific cylinder groups. Having different file systems
just means lets it pick from a smaller set of cylinder groups. If
your disk is so heavily loaded that this makes a difference, you
really want multiple spindles.

There are administrative reasons to split them up. For instance, the
backup for /usr is the FreeBSD CDROM set. / and /var I create backups
for, so /usr gets it's own file system, and /var lives on /. On a
second system, / and /usr are mounted read-only - well, they should be
- but /var has the web site on it, which gets updated at regular
intervals. So /var gets it's own file system, and /usr lives on /.

On my test system, which gets config files stored in perforce, I just
make everything one big file system.

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

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