From: Frank Mayhar Subject: Re: Concise description of disk layout? Date: Fri, 17 Apr 2009 11:49:26 -0700 Message-ID: <1239994166.7799.24.camel@bobble.smo.corp.google.com> References: <1239838392.12688.4.camel@bobble.smo.corp.google.com> <20090416002809.GG21586@mit.edu> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit To: linux-ext4@vger.kernel.org Return-path: Received: from smtp-out.google.com ([216.239.45.13]:53166 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760549AbZDQSt3 (ORCPT ); Fri, 17 Apr 2009 14:49:29 -0400 Received: from zps75.corp.google.com (zps75.corp.google.com [172.25.146.75]) by smtp-out.google.com with ESMTP id n3HInSsK015274 for ; Fri, 17 Apr 2009 11:49:28 -0700 Received: from [172.29.60.126] (bobble.smo.corp.google.com [172.29.60.126]) (authenticated bits=0) by zps75.corp.google.com with ESMTP id n3HInQv0032613 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT) for ; Fri, 17 Apr 2009 11:49:27 -0700 In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, 2009-04-17 at 18:30 +0000, Frank Mayhar wrote: > Sorry for the late reply. > > On Wed, 15 Apr 2009 20:28:09 -0400, Theodore Tso wrote: > > http://e2fsprogs.sourceforge.net/ext2intro.html > > > > but updated for ext4? > > Yeah, the "Physical Structure" section. I've read through some of the documents you pointed to and it sounds like the actual on-disk format hasn't changed significantly, i.e. block groups are laid out in basically the same way and the stuff within them is laid out in more or less the same way as in ext2/ext3; the major difference seems to be the allocation strategies embedded in the code itself. The new strategies simply mean that files and inodes are allocated more efficiently but not really in new places. Is this (more or less) correct or am I totally off-base? -- Frank Mayhar Google, Inc.