From: Theodore Tso Subject: Re: [PATCH] Ext4 Documentation updates. Date: Thu, 3 Jul 2008 21:19:37 -0400 Message-ID: <20080704011937.GK30506@mit.edu> References: <20080702172200.14990.37737.stgit@rx8> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org To: "Jose R. Santos" Return-path: Received: from www.church-of-our-saviour.ORG ([69.25.196.31]:43642 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753223AbYGDBTq (ORCPT ); Thu, 3 Jul 2008 21:19:46 -0400 Content-Disposition: inline In-Reply-To: <20080702172200.14990.37737.stgit@rx8> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed, Jul 02, 2008 at 12:22:00PM -0500, Jose R. Santos wrote: > From: Jose R. Santos > > Ext4 Documentation updates. > > Some of the information in Documentation/filesystems/ext4.txt is out > of date and in need of an update. > > Signed-off-by: Jose R. Santos Here are some changes I have added to further update/correct/clarify the ext4.txt file: - Ted diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt index 4424266..574c96a 100644 --- a/Documentation/filesystems/ext4.txt +++ b/Documentation/filesystems/ext4.txt @@ -13,40 +13,45 @@ Mailing list: linux-ext4@vger.kernel.org 1. Quick usage instructions: =========================== - - Grab updated e2fsprogs from + - Compile and install the latest version of e2fsprogs (at least + 1.41-WIP-0617) from: + ftp://ftp.kernel.org/pub/linux/kernel/people/tytso/e2fsprogs-interim/ or grab the latest git repository from: + git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git - - Create a new filesystem and set the "test_fs" extended option: + - Create a new filesystem using the ext4dev filesystem type: - # mke2fs -j -E test_fs /dev/hda1 + # mke2fs -t ext4dev /dev/hda1 - Or set the test_fs flag on an existing ext3 filesystem: + Or configure an existing ext3 filesystem to support extents and set + the test_fs flag to indicate that it's ok for an in-development + filesystem to touch this filesystem: - # debugfs -w /dev/sda5 - debugfs 1.41-WIP (17-Jun-2008) - debugfs: set_super_value s_flags 4 - debugfs: quit + # tune2fs -O extents -E test_fs /dev/hda1 - - Mounting: + If the filesystem was created with 128 byte inodes, it can be + converted to use 256 byte for greater efficiency via: - # mount /dev/hda1 /wherever -t ext4dev + # tune2fs -I 256 /dev/hda1 - - To disable extents: + (Note: we currently do not have tools to convert an ext4dev + filesystem back to ext3; so please do not do try this on production + filesystems.) - # mount /dev/hda1 /wherever -t ext4dev -o noextents + - Mounting: - - The filesystem is compatible with the ext3 driver until you add a file - which has extents (ie: `mount -o extents', then create a file). + # mount -t ext4dev /dev/hda1 /wherever - When comparing performance with other filesystems, remember that - ext3/4 by default offers higher data integrity guarantees than most. So - when comparing with a metadata-only journalling filesystem, use `mount -o - data=writeback'. And you might as well use `mount -o nobh' too along - with it. Making the journal larger than the mke2fs default often helps - performance with metadata-intensive workloads. + ext3/4 by default offers higher data integrity guarantees than most. + So when comparing with a metadata-only journalling filesystem, such + as ext3, use `mount -o data=writeback'. And you might as well use + `mount -o nobh' too along with it. Making the journal larger than + the mke2fs default often helps performance with metadata-intensive + workloads. 2. Features =========== @@ -67,17 +72,13 @@ Mailing list: linux-ext4@vger.kernel.org * ability to pack bitmaps and inode tables into larger virtual groups via the flex_bg feature * large file support - -2.2 Previously available, soon to be enabled by default by "mkefs.ext4":