From: Ric Wheeler Subject: Re: ext3 default journal mode Date: Thu, 23 Jul 2009 09:14:29 -0400 Message-ID: <4A686235.3060508@redhat.com> References: <4A63DB89.2060306@redhat.com> <20090720212904.GI2416@mit.edu> <20090720230402.GB26687@shell> <20090721020050.GK2416@mit.edu> <20090721174406.GA28383@shell> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Theodore Tso , Ric Wheeler , "linux-ext4@vger.kernel.org" , "Stephen C. Tweedie" , Eric Sandeen , Andreas Dilger , Chris Mason , Josef Bacik , Mingming Cao To: Valerie Aurora Return-path: Received: from mx2.redhat.com ([66.187.237.31]:37416 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753704AbZGWNOn (ORCPT ); Thu, 23 Jul 2009 09:14:43 -0400 In-Reply-To: <20090721174406.GA28383@shell> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 07/21/2009 01:44 PM, Valerie Aurora wrote: > 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 > I certainly agree - this is a vast improvement over what we have today, thanks! Ric