From owner-freebsd-current@FreeBSD.ORG Thu May 25 18:38:13 2006 Return-Path: X-Original-To: current@freebsd.org Delivered-To: freebsd-current@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 3568B16A989; Thu, 25 May 2006 18:38:13 +0000 (UTC) (envelope-from ATRENS@nortel.com) Received: from zrtps0kn.nortel.com (zrtps0kn.nortel.com [47.140.192.55]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8A16143D48; Thu, 25 May 2006 18:38:12 +0000 (GMT) (envelope-from ATRENS@nortel.com) Received: from zcarhxm2.corp.nortel.com (zcarhxm2.corp.nortel.com [47.129.230.99]) by zrtps0kn.nortel.com (Switch-2.2.6/Switch-2.2.0) with ESMTP id k4PIbjm22235; Thu, 25 May 2006 14:37:45 -0400 (EDT) Received: from [10.0.10.2] ([47.128.166.148] RDNS failed) by zcarhxm2.corp.nortel.com with Microsoft SMTPSVC(6.0.3790.1830); Thu, 25 May 2006 14:37:35 -0400 Message-ID: <4475F967.5040806@nortel.com> Date: Thu, 25 May 2006 14:37:27 -0400 From: "Andrew Atrens" User-Agent: Mozilla Thunderbird 1.0.7 (X11/20051129) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Olivier Gautherot References: <3981.1148578569@critter.freebsd.dk> <4475EFC1.1020504@nortel.com> <1148580598.4475f2f677197@imp2-g19.free.fr> In-Reply-To: <1148580598.4475f2f677197@imp2-g19.free.fr> X-Enigmail-Version: 0.93.0.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 25 May 2006 18:37:35.0956 (UTC) FILETIME=[4ADC2140:01C6802A] X-Mailman-Approved-At: Thu, 25 May 2006 18:43:17 +0000 Cc: Alexander Leidinger , Poul-Henning Kamp , small@freebsd.org, current@freebsd.org Subject: Re: FreeBSD's embedded agenda X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 25 May 2006 18:38:18 -0000 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi Olivier, Olivier Gautherot wrote: > 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 ;-) Yes, exactly... that's precisely what 'wear-leveling' is meant to do .. I think I mentioned wear-leveling further back in the email chain .. Yes, you definitely want wear-leveling. The debate is whether the filesystem knows about it, versus it being managed by a lower level 'driver'. Andrew. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (FreeBSD) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFEdfln8It2CaCdeMwRAo/kAJ0R6Wx5XGXscCaiJPKXcAMH2hfkYwCfeOtL s6pOk3K0jcjboPbO/pPnlSM= =95q/ -----END PGP SIGNATURE-----