From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964803AbWAWFim (ORCPT ); Mon, 23 Jan 2006 00:38:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964802AbWAWFil (ORCPT ); Mon, 23 Jan 2006 00:38:41 -0500 Received: from H190.C26.B96.tor.eicat.ca ([66.96.26.190]:48263 "EHLO moraine.clusterfs.com") by vger.kernel.org with ESMTP id S964803AbWAWFil (ORCPT ); Mon, 23 Jan 2006 00:38:41 -0500 Date: Sun, 22 Jan 2006 22:38:38 -0700 From: Andreas Dilger To: Andrew Morton Cc: sho@tnes.nec.co.jp, ext2-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [Ext2-devel] [PATCH] ext3: Extends blocksize up to pagesize Message-ID: <20060123053838.GM4124@schatzie.adilger.int> Mail-Followup-To: Andrew Morton , sho@tnes.nec.co.jp, ext2-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org References: <000001c61c30$00814e80$4168010a@bsd.tnes.nec.co.jp> <20060118185249.GN4124@schatzie.adilger.int> <20060120231016.40b40fd7.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060120231016.40b40fd7.akpm@osdl.org> User-Agent: Mutt/1.4.1i X-GPG-Key: 1024D/0D35BED6 X-GPG-Fingerprint: 7A37 5D79 BF1B CECA D44F 8A29 A488 39F5 0D35 BED6 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Jan 20, 2006 23:10 -0800, Andrew Morton wrote: > Andreas Dilger wrote: > > > > On Jan 18, 2006 22:06 +0900, Takashi Sato wrote: > > > As a disk tends to get large, a disk storage has had a capacity to > > > supply multi-TB. But now, ext3 can't support more than 8TB filesystem > > > when blocksize is 4KB. That's why I think ext3 needs to be > > > more than 8TB. > > > > > > Therefore I think filesystem size can increase on architectures > > > which has more than 4KB pagesize by extending blocksize to pagesize on > > > ext3. For example, the following is in case of ia64. (Blocksize have > > > already been supported up to pagesize on ext2. Why is the max blocksize > > > restricted to 4KB on ext3?) > > > > > > Max filesystem size on ia64: > > > Original :4096(blocksize) * 2^31 = 8TB > > > After modification [pagesize=16KB(default)]:16384(blocksize) * 2^31 = 32TB > > > After modification [pagesize=64KB(max)] :65536(blocksize) * 2^31 = 128TB > > > > Just for others' info - the fill_super change has been tested in the past > > by Sonny Rao at IBM also. e2fsprogs has supported this for a long time > > already. > > I have a vague memory that there's some piece of metadata (per-block-group > info, I think) which will overflow at 8kb blocksize. I say this in the > hope that you'll remmeber what it was ;) This is the group descriptor per-group blocks and inode free counts. The current mke2fs code limits the number of blocks and inodes per group to EXT2_MAX_BLOCKS_PER_GROUP (2^16 - 8) and (2^16 - EXT2_INODES_PER_BLOCK) so that this won't overflow. We still get linear growth of filesystem limits with blocksize, but not cubic growth that would otherwise be there. Bull has a patch which enlarges the group descriptor fields to allow more blocks and inodes per group. > I've rewritten ext3 directory readahead to use the generic pagecache > functions, so changes here shouldn't be needed. > > But I haven't yet got around to performance-testing it. > > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.16-rc1/2.6.16-rc1-mm2/broken-out/ext3_readdir-use-generic-readahead.patch Hmm, I'll have to take a look at that when I get a chance. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc.