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Date:      Thu, 30 Aug 2001 03:00:47 -0500
From:      Mike Meyer <mwm@mired.org>
To:        Trevin Chow <tmchow@sfu.ca>
Cc:        Mike Meyer <mwm@mired.org>, <questions@freebsd.org>
Subject:   Re: Performance tuning and adding RAM
Message-ID:  <15245.62127.417241.42347@guru.mired.org>
In-Reply-To: <20010830004542.A80091-100000@benny.geektank.org>
References:  <15245.52453.614096.245669@guru.mired.org> <20010830004542.A80091-100000@benny.geektank.org>

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Trevin Chow <tmchow@sfu.ca> types:
> On Thu, 30 Aug 2001, Mike Meyer wrote:
> 
> > For IDE drives, you disable this by setting the sysctl hw.ata.wc to 0,
> > but it has to be done from the boot loader at boot time. If you are
> > running 4.3-RELEASE, it's set off by default. If you're running
> > something prior to 4.3-RELEASE, you may not be able to set it at
> > all. The drive manufacturer may provide a DOS utility that will let
> > you turn it off as well.
> >
> > If you are using SCSI disks, you can use the camcontrol modepage
> > command to check and disable it. It's the WCE value on page 8; use
> > "camcontrol modepage daX -m 8 -e" to start an editor, change the 1 to
> > a 0, and then exit.
> What will provide a "bigger" performance boost? Soft updates or IDE Cache
> (hw.ata.wc)?

Oh, leaving the disk caching enabled is definitely faster. After all,
it's sort of like running a RAM disk through a slow interface. If
you're going to do that, mount your file systems async buy a UPS, and
make more frequent backups.

	<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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