From owner-freebsd-questions@FreeBSD.ORG Mon Jul 16 16:23:52 2007 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 424B016A403 for ; Mon, 16 Jul 2007 16:23:52 +0000 (UTC) (envelope-from peter.schuller@infidyne.com) Received: from proxy3.bredband.net (proxy3.bredband.net [195.54.101.73]) by mx1.freebsd.org (Postfix) with ESMTP id 02BA413C4B4 for ; Mon, 16 Jul 2007 16:23:51 +0000 (UTC) (envelope-from peter.schuller@infidyne.com) Received: from prometheus.scode.org (85.229.22.84) by proxy3.bredband.net (7.3.121.3) id 46815014005F7FF3 for freebsd-questions@freebsd.org; Mon, 16 Jul 2007 18:03:34 +0200 Received: from localhost (localhost [127.0.0.1]) by prometheus.scode.org (Postfix) with ESMTP id A5DFD1CC8E for ; Mon, 16 Jul 2007 19:57:23 +0200 (CEST) From: Peter Schuller To: freebsd-questions@freebsd.org Date: Mon, 16 Jul 2007 19:57:22 +0200 User-Agent: KMail/1.9.7 References: <4697C8DA.60705@wlink.com.np> <200707132345.l6DNjRb2023407@eunet.yu> <46990985.8020002@wlink.com.np> In-Reply-To: <46990985.8020002@wlink.com.np> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200707161957.23110.peter.schuller@infidyne.com> Subject: Re: FreeBSD-6.1 bootup hangs after power failure X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 16 Jul 2007 16:23:52 -0000 > One thing I find FreeBSD very fussy and sensitive in comparison to Linux > OSes is that whenever there is an power outage, something wrong is bound > to happen. Maybe, it was made to happen this way but living in here over > the other side of the world, we do have to face power outages despite > our best efforts. The problem with power outtages is that in the presence of write caching *all* bets are off. In practice I have found this a bigger problem with UFS2 than with e.g. reiserfs on Linux; possibly because the characteristics of disk i/o in those cases make it less probably to actually trigger a problem in practice (but this is just my speculation, but fits my experiences). But regardless, all bets *are* off in the event of a power outtage. Unless you have battery backed caching controllers, you will need to disable write caching (hw.ata.wc=0) in order to be safe - at the cost of performance. Alternatively for 7.0+ or CURRENT you can use ZFS which understands these things and will actually send cache flush commands to the drives on transaction commits, thus allowing safe operation in the event of a power failure, while not taking the performance hit associated with disabling write caching. -- / Peter Schuller PGP userID: 0xE9758B7D or 'Peter Schuller ' Key retrieval: Send an E-Mail to getpgpkey@scode.org E-Mail: peter.schuller@infidyne.com Web: http://www.scode.org