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Date:      Wed, 14 Mar 2001 08:29:56 -0600
From:      Mike Meyer <mwm@mired.org>
To:        Mark Ibell <marki@paradise.net.nz>
Cc:        Alfred Perlstein <bright@wintelcom.net>, Mars Attack <marsattack@cannoncreek.com>, Soren Schmidt <sos@freebsd.dk>, Peter Wemm <peter@netplex.com.au>, Helge Oldach <Helge.Oldach@de.origin-it.com>, oberman@es.net, mobile@FreeBSD.ORG, stable@FreeBSD.ORG
Subject:   Re: Disk I/O problem in 4.3-BETA
Message-ID:  <15023.32868.9995.327616@guru.mired.org>
In-Reply-To: <3AAF4DA0.C8DA9485@paradise.net.nz>
References:  <200103131007.f2DA73h54023@mobile.wemm.org> <01f001c0abaa$133e1680$4500a8c0@nomad> <20010313032635.Q29888@fw.wintelcom.net> <3AAF4DA0.C8DA9485@paradise.net.nz>

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Mark Ibell <marki@paradise.net.nz> types:
> What doesn't appear to have been mentioned is how exactly do we turn off
> write caching on SCSI drives. From poking around the best I could work
> out was to run 'camcontrol modepage da0 -m 0x08 -e -P 3' and set WCE to
> 0 where 0x08 comes from /usr/share/misc/scsi_modes.
> 
> Is this the correct way to do it?

Assuming you've got the right numbers for WCE, yes. Camcontrol is the
right tool.

> Also, is it okay to leave tagged queuing enabled? (I'm really starting
> to get paranoid after all this discussion!)

I'd say yes, as at least some of the drivers expect it to be there. I
think the critical thing is that the driver know when the data is
actually on the disk, so if tagged queueing doesn't interfere with
that, it's ok.

	<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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