From owner-freebsd-questions Thu Oct 4 12:49:29 2001 Delivered-To: freebsd-questions@freebsd.org Received: from guru.mired.org (okc-65-31-203-60.mmcable.com [65.31.203.60]) by hub.freebsd.org (Postfix) with SMTP id 535DC37B401 for ; Thu, 4 Oct 2001 12:49:21 -0700 (PDT) Received: (qmail 69745 invoked by uid 100); 4 Oct 2001 19:49:15 -0000 From: Mike Meyer MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <15292.48443.672916.539479@guru.mired.org> Date: Thu, 4 Oct 2001 14:49:15 -0500 To: "Magdalinin Kirill" Cc: questions@freebsd.org Subject: Re: turning off write cache on SCSI drive In-Reply-To: <125479656@toto.iv> X-Mailer: VM 6.90 under 21.1 (patch 14) "Cuyahoga Valley" XEmacs Lucid X-face: "5Mnwy%?j>IIV\)A=):rjWL~NB2aH[}Yq8Z=u~vJ`"(,&SiLvbbz2W`;h9L,Yg`+vb1>RG% *h+%X^n0EZd>TM8_IB;a8F?(Fb"lw'IgCoyM.[Lg#r\ Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Magdalinin Kirill types: > Hello, > some mail posts on softupdates says that turning off write cache is > prerequisite for it. They're generally talking about IDE drives. SCSI drives have tagged queuing, which means you're perfectly safe doing this. > How can I accomplish it on freebsd? As far as I know > there is camcontrol utility, but it's usage is quite > difficult for me to understand. camcontrol modepage da0 -m 8 -e -P X edit the page that comes up, and change the WCE: entry from 1 to 0. Do this four times, with X the last X being 0 and 3 > The other way I can think of it is turning it off > under Win2K. Yet how can I check write cache status > under FreeBSD? camcontrol modepage da0 -m 8 -P 0 will print the current value as the WCE line. Before doing *any* of this, check /var/run/dmesg.boot to see if tagged queuing is on for those drives. If it is, you should enable WCE, not disable it. You'll see a line like: da0: 40.000MB/s transfers (20.000MHz, offset 31, 16bit), Tagged Queueing Enabled meaning that you can leave - and probably want to enable - Write Cache for that drive. A drive without tagged queueing looks like: da2: 10.000MB/s transfers (10.000MHz, offset 15) (yeah, it's a very old, slow drive.....) http://www.mired.org/home/mwm/ Q: How do you make the gods laugh? A: Tell them your plans. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message