Date: Thu, 4 Oct 2001 14:49:15 -0500 From: Mike Meyer <mwm@mired.org> To: "Magdalinin Kirill" <bsdforumen@hotmail.com> Cc: questions@freebsd.org Subject: Re: turning off write cache on SCSI drive Message-ID: <15292.48443.672916.539479@guru.mired.org> In-Reply-To: <125479656@toto.iv>
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Magdalinin Kirill <bsdforumen@hotmail.com> 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.....) <mike -- Mike Meyer <mwm@mired.org> 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
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