From: tytso@mit.edu Subject: Re: fsck more often when powerfail is detected (was Re: wishful thinking about atomic, multi-sector or full MD stripe width, writes in storage) Date: Sun, 4 Apr 2010 13:39:12 -0400 Message-ID: <20100404173912.GF18524@thunk.org> References: <4A9F230F.40707@redhat.com> <4A9FA5F2.9090704@redhat.com> <4A9FC9B3.1080809@redhat.com> <4A9FCF6B.1080704@redhat.com> <20090907114534.GP23450@elf.ucw.cz> <20090907131026.GC32427@mit.edu> <20100404134729.GA1388@ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ric Wheeler , Krzysztof Halasa , Christoph Hellwig , Mark Lord , Michael Tokarev , david@lang.hm, NeilBrown , Rob Landley , Florian Weimer , Goswin von Brederlow , kernel list , Andrew Morton , mtk.manpages@gmail.com, rdunlap@xenotime.net, linux-doc@vger.kernel.org, linux-ext4@vger.kernel.org, corbet@lwn.net To: Pavel Machek Return-path: Received: from THUNK.ORG ([69.25.196.29]:40469 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752052Ab0DDRkn (ORCPT ); Sun, 4 Apr 2010 13:40:43 -0400 Content-Disposition: inline In-Reply-To: <20100404134729.GA1388@ucw.cz> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Sun, Apr 04, 2010 at 03:47:29PM +0200, Pavel Machek wrote: > > Yes, but ext3 does not enable barriers by default (the patch has been > > submitted but akpm has balked because he doesn't like the performance > > degredation and doesn't believe that Chris Mason's "workload of doom" > > is a common case). Note though that it is possible for dirty blocks > > to remain in the track buffer for *minutes* without being written to > > spinning rust platters without a barrier. > > So we do wrong thing by default. Another reason to do fsck more often > when powerfails are present? Or migrate to ext4, which does use barriers by defaults, as well as journal-level checksumming. :-) As far as changing the default to enable barriers for ext3, you'll need to talk to akpm about that; he's the one who has been against it in the past. - Ted