From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 24 Jun 2001 19:19:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 24 Jun 2001 19:19:31 -0400 Received: from humbolt.nl.linux.org ([131.211.28.48]:42506 "EHLO humbolt.nl.linux.org") by vger.kernel.org with ESMTP id ; Sun, 24 Jun 2001 19:19:16 -0400 Content-Type: text/plain; charset=US-ASCII From: Daniel Phillips To: "Albert D. Cahalan" , linux-kernel@vger.kernel.org Subject: Re: FAT32 superiority over ext2 :-) Date: Mon, 25 Jun 2001 01:22:17 +0200 X-Mailer: KMail [version 1.2] Cc: viro@math.psu.edu, phillips@bonn-fries.net, chaffee@cs.berkeley.edu, storner@image.dk, mnalis-umsdos@voyager.hr In-Reply-To: <200106242254.f5OMsxQ405511@saturn.cs.uml.edu> In-Reply-To: <200106242254.f5OMsxQ405511@saturn.cs.uml.edu> MIME-Version: 1.0 Message-Id: <0106250122170H.00430@starship> Content-Transfer-Encoding: 7BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Monday 25 June 2001 00:54, Albert D. Cahalan wrote: > By dumb luck (?), FAT32 is compatible with the phase-tree algorithm > as seen in Tux2. This means it offers full data integrity. > Yep, it whips your typical journalling filesystem. Look at what > we have in the superblock (boot sector): > > __u32 fat32_length; /* sectors/FAT */ > __u16 flags; /* bit 8: fat mirroring, low 4: active fat */ > __u8 version[2]; /* major, minor filesystem version */ > __u32 root_cluster; /* first cluster in root directory */ > __u16 info_sector; /* filesystem info sector */ > > All in one atomic write, one can... > > 1. change the active FAT > 2. change the root directory > 3. change the free space count > > That's enough to atomically move from one phase to the next. > You create new directories in the free space, and make FAT > changes to an inactive FAT copy. Then you write the superblock > to atomically transition to the next phase. Yes, FAT is what inspired me to go develop the algorithm. However, two words: 'lost clusters'. Now that may just be an implemenation detail ;-) -- Daniel