From owner-freebsd-stable@FreeBSD.ORG Fri Jul 15 18:54:23 2005 Return-Path: X-Original-To: freebsd-stable@freebsd.org 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 2169616A41C; Fri, 15 Jul 2005 18:54:23 +0000 (GMT) (envelope-from jmg@hydrogen.funkthat.com) Received: from hydrogen.funkthat.com (gate.funkthat.com [69.17.45.168]) by mx1.FreeBSD.org (Postfix) with ESMTP id CD4FB43D53; Fri, 15 Jul 2005 18:54:18 +0000 (GMT) (envelope-from jmg@hydrogen.funkthat.com) Received: from hydrogen.funkthat.com (localhost.funkthat.com [127.0.0.1]) by hydrogen.funkthat.com (8.13.3/8.13.3) with ESMTP id j6FIsEhg026552; Fri, 15 Jul 2005 11:54:14 -0700 (PDT) (envelope-from jmg@hydrogen.funkthat.com) Received: (from jmg@localhost) by hydrogen.funkthat.com (8.13.3/8.13.3/Submit) id j6FIsDtR026551; Fri, 15 Jul 2005 11:54:13 -0700 (PDT) (envelope-from jmg) Date: Fri, 15 Jul 2005 11:54:13 -0700 From: John-Mark Gurney To: Matthias Buelow Message-ID: <20050715185413.GI37261@funkthat.com> Mail-Followup-To: Matthias Buelow , Kevin Oberman , freebsd-stable@freebsd.org, freebsd-questions@freebsd.org References: <42D6B117.5080302@plab.ku.dk> <20050714191449.A8A615D07@ptavv.es.net> <20050714195253.GA23666@drjekyll.mkbuelow.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050714195253.GA23666@drjekyll.mkbuelow.net> User-Agent: Mutt/1.4.2.1i X-Operating-System: FreeBSD 5.4-RELEASE-p1 i386 X-PGP-Fingerprint: B7 EC EF F8 AE ED A7 31 96 7A 22 B3 D8 56 36 F4 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html Cc: freebsd-stable@freebsd.org, freebsd-questions@freebsd.org Subject: Re: dangerous situation with shutdown process X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: John-Mark Gurney List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 15 Jul 2005 18:54:23 -0000 Matthias Buelow wrote this message on Thu, Jul 14, 2005 at 21:52 +0200: > >The problem is that disks lie about whether they have actually written > >data. If the power goes off before the data is in cache, it's lost. > > No, the problem is that FreeBSD doesn't implement request barriers > and that softupdates is flawed by design and seemingly could not > make use of them, even if they were available (because, as I > understand it, it relies on a total ordering of all writes, unlike > the partial ordering necessary for a journalled fs). even request barries will not save the fs in a power loss if the track that is getting flushed durning a power loss... Some other FreeBSD folk has a reproducable case of where blocks that were not written to on ATA hardware got trashed after a power loss... With non-written to sectors getting trashed with the cache enabled, barriers don't mean squat... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."