Date: Wed, 7 Dec 2005 17:30:13 -0500 From: Martin Cracauer <cracauer@cons.org> To: Dieter <freebsd@sopwith.solgatos.com> Cc: freebsd-questions@freebsd.org Subject: Re: Disk write caching, hw.ata.wc and atacontrol disagree Message-ID: <20051207173013.A29261@cons.org> In-Reply-To: <200512072205.WAA17272@sopwith.solgatos.com>; from freebsd@sopwith.solgatos.com on Wed, Dec 07, 2005 at 02:05:40PM %2B0000 References: <200512072205.WAA17272@sopwith.solgatos.com>
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Dieter wrote on Wed, Dec 07, 2005 at 02:05:40PM +0000: > I'm trying to turn off the evil data corrupting on-disk write cache. > > I added hw.ata.wc=0 to /boot/loader.conf and rebooted. > > # sysctl hw.ata.wc > hw.ata.wc: 0 > > So far so good. But! atacontrol cap ad4 says: > > Feature Support Enable Value Vendor > write cache yes yes > > So hw.ata.wc thinks that the disk write cache is off, > but atacontrol cap thinks the disk write cache is on? I remember this is working but there was a reporting problem in atacontrol. You should easily be able to tell whether it is on or off by the write performance. It should plummet by a factor of 4 or so. cstream -i- -o/mnt/wherever/tmpfile -v1 Martin -- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Martin Cracauer <cracauer@cons.org> http://www.cons.org/cracauer/ FreeBSD - where you want to go, today. http://www.freebsd.org/
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