From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757789AbYDAKCJ (ORCPT ); Tue, 1 Apr 2008 06:02:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756035AbYDAKB6 (ORCPT ); Tue, 1 Apr 2008 06:01:58 -0400 Received: from smtp.nokia.com ([192.100.122.230]:23129 "EHLO mgw-mx03.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754922AbYDAKB5 (ORCPT ); Tue, 1 Apr 2008 06:01:57 -0400 Message-ID: <47F2071A.6010406@yandex.ru> Date: Tue, 01 Apr 2008 12:57:46 +0300 From: Artem Bityutskiy User-Agent: Thunderbird 2.0.0.12 (X11/20080226) MIME-Version: 1.0 To: Tomasz Chmielewski CC: LKML , penberg@cs.helsinki.fi, =?UTF-8?B?SsO2cm4gRW5nZWw=?= , ext-adrian.hunter@nokia.com, jwboyer@gmail.com Subject: Re: UBIFS vs Logfs (was [RFC PATCH] UBIFS - new flash file system) References: <47F1EC20.6050600@wpkg.org> <47F1F644.4060000@yandex.ru> <47F202D9.20405@wpkg.org> In-Reply-To: <47F202D9.20405@wpkg.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-OriginalArrivalTime: 01 Apr 2008 10:01:37.0142 (UTC) FILETIME=[5FA0C160:01C893DF] X-Nokia-AV: Clean Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Tomasz Chmielewski wrote: > Such as? ext3 for example. > Flash (also on block devices) is slow and expensive (when compared to > modern hard disks) and therefore compression is *very* useful here. Well, if you are ready to trade performance to compression, then well, go ahead :-) May be I used too strong wording, but I wanted to say then use raw flash then. But I'd also consider implementing compression support for a block based FS. Reiser4 claimed to have it for example. > Do you mean using hacks like block2mtd? It's hacky, and pretty hard to > boot a system this way (need to build own initramfs, with a static > block2mtd or loads of libraries - not something an average user would > like to do; no distro supports it; updating a kernel would be a pain etc.). Well, ok, it still sounds strange for me, but you may use JFFS2 and UBIFS with block2mtd as well if you really want to. > True. > Unfortunately, there is no way to access flash directly on flash-based > block devices (USB-sticks, IDE-flash disks, SSD disks etc.). Yeah, that's a pity :-( > Unfortunately, traditional filesystems were rather designed for rotating > media / cheap disks (no transparent compression; tend to accumulate > writes in one area of the disk - more on that - below). Sure. > Performance is only one factor in the equation. Other factors are: cost > and reliability. > > I speak from experience: flash-based block devices tend to have poor > wear-levelling (at least Transcend IDE-flash disks). > To reproduce: > - format a 2 GB Transcend IDE-flash disk with ext3 > - write a small file (50-100 kB) > - update that file ~several hundred thousand times - as you finish, > IDE-flash disk will have 200-300 badblocks Yeah, that's bad. But if you have a bad FTL, surely there is not guarantee a flash FS will help? Isn't it better to use better hardware? We did some experiments with MMC cards and we were unable to wear them out with re-writing the same sectors again and again. This suggests there _is_ better FTL hardware then that USB stick you was using. Anyway, your original mail said Logfs can work with block devices. My answer - UBIFS too, but this is very strange to do this IMO. But OK, it might is not senseless, sorry for the wording. :-) -- Best Regards, Artem Bityutskiy (Артём Битюцкий)