From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754036AbYLGUcN (ORCPT ); Sun, 7 Dec 2008 15:32:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752440AbYLGUb4 (ORCPT ); Sun, 7 Dec 2008 15:31:56 -0500 Received: from www.church-of-our-saviour.org ([69.25.196.31]:41282 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752342AbYLGUby (ORCPT ); Sun, 7 Dec 2008 15:31:54 -0500 Date: Sun, 7 Dec 2008 13:39:16 -0500 From: Theodore Tso To: Eric Sandeen Cc: Christoph Hellwig , Harald Arnesen , linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org Subject: Re: [ext4] Documentation patch Message-ID: <20081207183916.GB15998@mit.edu> Mail-Followup-To: Theodore Tso , Eric Sandeen , Christoph Hellwig , Harald Arnesen , linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org References: <8763m3u9kv.fsf@basilikum.skogtun.org> <20081201165700.GA26680@infradead.org> <493425DC.1010008@redhat.com> <20081201205828.GA20069@mit.edu> <20081206222534.GJ1323@mit.edu> <493B0BAD.10004@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <493B0BAD.10004@redhat.com> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@mit.edu X-SA-Exim-Scanned: No (on thunker.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Good points. OK, how about this? - When comparing performance with other filesystems, it's always important to try multiple workloads; very often a subtle change in a workload parameter can completely change the ranking of which filesystems do well compared to others. When comparing versus ext3, note that ext4 enables write barriers by default, while ext3 does not enable write barriers by default. So it is useful to use explicitly specify whether barriers are enabled or not when via the '-o barriers=[0|1]' mount option for both ext3 and ext4 filesystems for a fair comparison. When tuning ext3 for best benchmark numbers, it is often worthwhile to try changing the data journaling mode; '-o data=writeback,nobh' can be faster for some workloads. (Note however that running mounting with data=writeback can potentially leave stale data exposed in recently written files in case of an unclean shutdown, which could be a security exposure in some situations.) Configuring the filesystem with a large journal can also be helpful for metadata-intensive workloads. - Ted