Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751313AbWAVSl0 (ORCPT ); Sun, 22 Jan 2006 13:41:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751314AbWAVSl0 (ORCPT ); Sun, 22 Jan 2006 13:41:26 -0500 Received: from rwcrmhc11.comcast.net ([204.127.198.35]:46742 "EHLO rwcrmhc11.comcast.net") by vger.kernel.org with ESMTP id S1751313AbWAVSlZ (ORCPT ); Sun, 22 Jan 2006 13:41:25 -0500 Message-ID: <43D3D190.8010104@comcast.net> Date: Sun, 22 Jan 2006 13:40:16 -0500 From: John Richard Moser User-Agent: Mozilla Thunderbird 1.0.7 (X11/20051013) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Jan Engelhardt CC: linux-kernel@vger.kernel.org Subject: Re: soft update vs journaling? References: <43D3295E.8040702@comcast.net> In-Reply-To: X-Enigmail-Version: 0.92.1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2809 Lines: 70 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Jan Engelhardt wrote: >>Unfortunately, journaling uses a chunk of space. Imagine a journal on a >>USB flash stick of 128M; a typical ReiserFS journal is 32 megabytes! >>Sure it could be done in 8 or 4 or so; or (in one of my file system >>designs) a static 16KiB block could reference dynamicly allocated >>journal space, allowing the system to sacrifice performance and shrink >>the journal when more space is needed. Either way, slow media like >>floppies will suffer, HARD; and flash devices will see a lot of >>write/erase all over the journal area, causing wear on that spot. > > > - Smallest reiserfs3 journal size is 513 blocks - some 2 megabytes, > which would be ok with me for a 128meg drive. > Most of the time you need vfat anyway for your flashstick to make > useful use of it on Windows. > > - reiser4's journal is even smaller than reiser3's with a new fresh > filesystem - same goes for jfs and xfs (below 1 megabyte IIRC) > Nice, but does not solve. . . > - I would not use a journalling filesystem at all on media that degrades > faster as harddisks (flash drives, CD-RWs/DVD-RWs/RAMs). > There are specially-crafted filesystems for that, mostly jffs and udf. > Yes. They'll degrade very, very fast. This is where Soft Update would have an advantage. Another issue here is we can't just slap a journal onto vfat, for all those flash devices that we want to share with Windows. > - You really need a hell of a power fluctuation to get a disk crippled. > Just powering off (and potentially on after a few milliseconds) did > (in my cases) just stop a disk write whereever it happened to be, > and that seemed easily correctable. Yeah, I never said you could cripple a disk with power problems. You COULD destroy a NAND in a flash device by nuking the thing with 10000000000000 writes to the same area. > > > Jan Engelhardt - -- All content of all messages exchanged herein are left in the Public Domain, unless otherwise explicitly stated. Creative brains are a valuable, limited resource. They shouldn't be wasted on re-inventing the wheel when there are so many fascinating new problems waiting out there. -- Eric Steven Raymond -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFD09GOhDd4aOud5P8RAr1lAJ9fGMSJOd4QALc4nCbx+jDLgTlijwCbBM94 r60oZO/x2Q0xEWeF9sp9Vz8= =63vo -----END PGP SIGNATURE----- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/