From: Valerie Aurora Subject: Re: ext3 default journal mode Date: Tue, 21 Jul 2009 13:44:07 -0400 Message-ID: <20090721174406.GA28383@shell> References: <4A63DB89.2060306@redhat.com> <20090720212904.GI2416@mit.edu> <20090720230402.GB26687@shell> <20090721020050.GK2416@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ric Wheeler , "linux-ext4@vger.kernel.org" , "Stephen C. Tweedie" , Eric Sandeen , Andreas Dilger , Chris Mason , Josef Bacik , Mingming Cao To: Theodore Tso Return-path: Received: from mx1.redhat.com ([66.187.233.31]:37627 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751446AbZGURot (ORCPT ); Tue, 21 Jul 2009 13:44:49 -0400 Content-Disposition: inline In-Reply-To: <20090721020050.GK2416@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, Jul 20, 2009 at 10:00:50PM -0400, Theodore Tso wrote: > On Mon, Jul 20, 2009 at 07:04:03PM -0400, Valerie Aurora wrote: > > > > I think it's extremely accurate and detailed, but too long - people's > > brains turn off after about the 15th line or so. Here's an attempt to > > distill your description down and refer out to another document (which > > one?) for people who want to learn more. > > Fair enough; I've created an external document here: > > http://ext4.wiki.kernel.org/index.php/Ext3_Data%3DOrdered_vs_Data%3DWriteback_mode > > Comments? Nice! > > config EXT3_DEFAULTS_TO_ORDERED > > bool "Default to 'data=ordered' in ext3" > > depends on EXT3_FS > > help > > > > If the mount options for an ext3 filesystem do not > > include a journal mode, mount it in "data=ordered" mode. > > Let me give a try at this: > > The journal mode options for ext3 have different tradeoffs > between when data is guaranteed to be on disk and > performance. The use of "data=writeback" can cause > unwritten data to appear in files after an system crash or > power failure, which can be a security issue. However, > "data=ordered" mode can also result in major performance > problems, including seconds-long delays before an fsync() > call returns. For details, see: > > http://ext4.wiki.kernel.org/index.php/Ext3_Data%3DOrdered_vs_Data%3DWriteback_mode > > If you have been historically happy with ext3's performance, > data=ordered mode will be a safe choice and you should > answer "y" here. If you understand the reliability and data > privacy issues of data=writeback and are willing to make > that trade off, answer "n". This is great. Ship it! -VAL