From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Mon, 04 Feb 2008 06:26:03 -0800 (PST) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.168.28]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id m14EPrWK030777 for ; Mon, 4 Feb 2008 06:25:54 -0800 Received: from sandeen.net (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id B5DD2D816A6 for ; Mon, 4 Feb 2008 06:26:12 -0800 (PST) Received: from sandeen.net (sandeen.net [209.173.210.139]) by cuda.sgi.com with ESMTP id to2W1dZ7BVrDaSZk for ; Mon, 04 Feb 2008 06:26:12 -0800 (PST) Message-ID: <47A72061.3010800@sandeen.net> Date: Mon, 04 Feb 2008 08:25:37 -0600 From: Eric Sandeen MIME-Version: 1.0 Subject: Re: RAID needs more to survive a power hit, different /boot layout for example (was Re: draft howto on making raids for surviving a disk crash) References: <47A612BE.5050707@pobox.com> <47A623EE.4050305@msgid.tls.msk.ru> <47A62A17.70101@pobox.com> <47A6DA81.3030008@msgid.tls.msk.ru> <47A6EFCF.9080906@pobox.com> <47A7188A.4070005@msgid.tls.msk.ru> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: Justin Piszcz Cc: Michael Tokarev , Moshe Yudkowsky , linux-raid@vger.kernel.org, xfs@oss.sgi.com Justin Piszcz wrote: > Why avoid XFS entirely? > > esandeen, any comments here? Heh; well, it's the meme. see: http://oss.sgi.com/projects/xfs/faq.html#nulls and note that recent fixes have been made in this area (also noted in the faq) Also - the above all assumes that when a drive says it's written/flushed data, that it truly has. Modern write-caching drives can wreak havoc with any journaling filesystem, so that's one good reason for a UPS. If the drive claims to have metadata safe on disk but actually does not, and you lose power, the data claimed safe will evaporate, there's not much the fs can do. IO write barriers address this by forcing the drive to flush order-critical data before continuing; xfs has them on by default, although they are tested at mount time and if you have something in between xfs and the disks which does not support barriers (i.e. lvm...) then they are disabled again, with a notice in the logs. Note also that ext3 has the barrier option as well, but it is not enabled by default due to performance concerns. Barriers also affect xfs performance, but enabling them in the non-battery-backed-write-cache scenario is the right thing to do for filesystem integrity. -Eric > Justin. >