From: Jan Kara Subject: Re: Ext3 behavior on power failure Date: Wed, 28 Mar 2007 17:00:03 +0200 Message-ID: <20070328150003.GE29587@duck.suse.cz> References: <4603B03E.7080302@emc.com> <20070328124015.GG14935@atrey.karlin.mff.cuni.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: jakj@j-a-k-j.com, jack@suse.cz, ric@popimap.lss.emc.com, ext3-users@redhat.com, linux-ext4@vger.kernel.org, csar@stanford.edu To: armangau_philippe@emc.com Return-path: Received: from styx.suse.cz ([82.119.242.94]:56577 "EHLO duck.suse.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932183AbXC1OxM (ORCPT ); Wed, 28 Mar 2007 10:53:12 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Wed 28-03-07 10:17:33, armangau_philippe@emc.com wrote: > In my case the disk cache is not a problem - We use an emc disk array > the write cache is protected - > Once the data has made over the disk array we can assume it is safe - Then if you are able to reproduce the situation that not all data is written after fsync(); poweroff; that is a bug worth reporting.. Honza > > -----Original Message----- > From: John Anthony Kazos Jr. [mailto:jakj@j-a-k-j.com] > Sent: Wednesday, March 28, 2007 9:17 AM > To: Jan Kara > Cc: wheeler, richard; armangau, philippe; ext3-users@redhat.com; > linux-ext4@vger.kernel.org; csar@stanford.edu > Subject: Re: Ext3 behavior on power failure > > > If you fsync() your data, you are guaranteed that also your data are > > safely on disk when fsync returns. So what is the question here? > > Pardon a newbie's intrusion, but I do know this isn't true. There is a > window of possible loss because of the multitude of layers of caching, > especially within the drive itself. Unless there is a > super_duper_fsync() > that is able to actually poll the hardware and get a confirmation that > the > internal buffers are purged? > -- Jan Kara SuSE CR Labs