From owner-freebsd-small@FreeBSD.ORG Thu May 25 18:10:00 2006 Return-Path: X-Original-To: small@freebsd.org Delivered-To: freebsd-small@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 0D4D516A606; Thu, 25 May 2006 18:10:00 +0000 (UTC) (envelope-from olivier@gautherot.net) Received: from smtp2-g19.free.fr (smtp2-g19.free.fr [212.27.42.28]) by mx1.FreeBSD.org (Postfix) with ESMTP id 77AD743D4C; Thu, 25 May 2006 18:09:59 +0000 (GMT) (envelope-from olivier@gautherot.net) Received: from imp2-g19.free.fr (imp2-g19.free.fr [212.27.42.2]) by smtp2-g19.free.fr (Postfix) with ESMTP id B9C567118D; Thu, 25 May 2006 20:09:58 +0200 (CEST) Received: by imp2-g19.free.fr (Postfix, from userid 33) id 8BF8061A3; Thu, 25 May 2006 20:09:58 +0200 (CEST) Received: from 200.54.71.227 ([200.54.71.227]) by imp2-g19.free.fr (IMP) with HTTP for ; Thu, 25 May 2006 20:09:58 +0200 Message-ID: <1148580598.4475f2f677197@imp2-g19.free.fr> Date: Thu, 25 May 2006 20:09:58 +0200 From: Olivier Gautherot To: Andrew Atrens References: <3981.1148578569@critter.freebsd.dk> <4475EFC1.1020504@nortel.com> In-Reply-To: <4475EFC1.1020504@nortel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit User-Agent: Internet Messaging Program (IMP) 3.2.5 X-Originating-IP: 200.54.71.227 Cc: Alexander Leidinger , Poul-Henning Kamp , small@freebsd.org, current@freebsd.org Subject: Re: FreeBSD's embedded agenda X-BeenThere: freebsd-small@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Dedicated and Embedded Systems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 25 May 2006 18:10:10 -0000 Hi Andrew! > [...] > > The reason Flash Adaptation Layers came about in the first place > > is that W95 didn't support anything but FAT. > > > Hmm. I was thinking about partitioning the problem actually. Make flash > look like a disk and then you can put any filesystem on it that you > want. Seems a heck of a lot simpler .. and I'm not sure if I see any > drawbacks to doing it that way ... The drawback is the following: what would happen if you had an application opening-writing-closing a file in /var/log on a regular basis? The block would decay with time, with chances that your log even gets corrupted. That's why Flash drivers have to spread write accesses across the device (what FFS doesn't naturally do). Also, there is a constraint regarding the changes allowed: on NAND flash, you can write a 0 on a bit but have to erase the full block to write a 1 back. Don't forget that Flash doesn't suffer from mechanical delays so there is no harm in fragmenting the filesystem: this would be another feature. My cent worth ;-) -- Olivier Gautherot olivier@gautherot.net Tel: +56 8 730 9361