From owner-freebsd-small@FreeBSD.ORG Thu May 25 20:13:27 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 DEA3916B985; Thu, 25 May 2006 20:13:27 +0000 (UTC) (envelope-from imp@bsdimp.com) Received: from harmony.bsdimp.com (vc4-2-0-87.dsl.netrack.net [199.45.160.85]) by mx1.FreeBSD.org (Postfix) with ESMTP id DE89D43D78; Thu, 25 May 2006 20:13:23 +0000 (GMT) (envelope-from imp@bsdimp.com) Received: from localhost (localhost.village.org [IPv6:::1] (may be forged)) by harmony.bsdimp.com (8.13.4/8.13.4) with ESMTP id k4PKBY3G036813; Thu, 25 May 2006 14:11:34 -0600 (MDT) (envelope-from imp@bsdimp.com) Date: Thu, 25 May 2006 14:11:34 -0600 (MDT) Message-Id: <20060525.141134.221855237.imp@bsdimp.com> To: anderson@centtech.com From: "M. Warner Losh" In-Reply-To: <4476036F.4090302@centtech.com> References: <4350.1148583733@critter.freebsd.dk> <4476036F.4090302@centtech.com> X-Mailer: Mew version 4.2 on Emacs 21.3 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: Alexander@Leidinger.net, phk@phk.freebsd.dk, 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 20:13:38 -0000 In message: <4476036F.4090302@centtech.com> Eric Anderson writes: : Poul-Henning Kamp wrote: : > In message <4475EFC1.1020504@nortel.com>, "Andrew Atrens" writes: : > : >>>> Said kernel would have a low level driver that makes plain : >>>> old flash chips look (and behave) like a disk. It would support : >>>> wear-levelling, [...] : >>>> : >>>> Then you could throw FFS on top of that. : >>> This is exactly what you do not want to do. : >>> : >>> You want to write a flash friendly filesystem which knows what : >>> a flash is, and which does the wear levelling internally. : >>> : >>> 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 main one is that the flash adaptation layer does not have the : > full information to work with for deciding wear-leveling decisions : > and the filesystem has no idea what the optimal block allocation : > strategy is for the flash device. : > : > Flash devices have no seek time penalty, and therefore the block : > allocation should focus on wear-leveling rather than seek time : > optimization. : > : : This sounds like an awefuly fun project to me. Is anyone (PHK?) willing : to help me with some of the FreeBSD kernel related issues? If so, I'd : like to work on this. I can help. I don't suffer from the NDA issues that phk has. Warner