From owner-freebsd-stable@FreeBSD.ORG Fri Jan 21 16:31:10 2005 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 19B4716A4CE for ; Fri, 21 Jan 2005 16:31:10 +0000 (GMT) Received: from postal3.es.net (postal3.es.net [198.128.3.207]) by mx1.FreeBSD.org (Postfix) with ESMTP id E978F43D2D for ; Fri, 21 Jan 2005 16:31:09 +0000 (GMT) (envelope-from oberman@es.net) Received: from ptavv.es.net ([198.128.4.29]) by postal3.es.net (Postal Node 3) with ESMTP (SSL) id IBA74465; Fri, 21 Jan 2005 08:31:09 -0800 Received: from ptavv (localhost [127.0.0.1]) by ptavv.es.net (Tachyon Server) with ESMTP id B01855D08; Fri, 21 Jan 2005 08:31:06 -0800 (PST) To: Mark Kirkwood In-reply-to: Your message of "Fri, 21 Jan 2005 20:53:12 +1300." <41F0B4E8.9090507@paradise.net.nz> Date: Fri, 21 Jan 2005 08:31:06 -0800 From: "Kevin Oberman" Message-Id: <20050121163106.B01855D08@ptavv.es.net> cc: freebsd-stable@freebsd.org cc: "Jim C. Nasby" Subject: Re: Disabling write-behind on IDE drives, and SMART X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 21 Jan 2005 16:31:10 -0000 > Date: Fri, 21 Jan 2005 20:53:12 +1300 > From: Mark Kirkwood > Sender: owner-freebsd-stable@freebsd.org > > Jim C. Nasby wrote: > > Question one: how do I disable write caching on IDE drives? I know the > > setting is hw.ata.wc=0, but where do I put that? In loader.conf? This is > > FreeBSD 4.10, btw. > > > In /boot/loader.conf will do it. > > > Also, has any thought been given to making the default 0, like it is for > > SCSI devices? I'm honestly surprised and disappointed that the default > > is speed over data integrity. > I think it was trialled in 4.3 then changed for 4.4 (according to the > handbook, the performance hit was considered to be too high) Having been involved in the 4.x flip-flop, the performance cost on some systems can be HUGE! Backing up my laptop (40 GB) went from 40 minutes to five hours when the write cache was turned off. On the other hand, it is a real risk, especially when combined with softupdates. For servers that lack solid backup power (not a 10 minute UPS), I would probably turn it off. But for most systems it is probably worth the risks. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634