From owner-cvs-all@FreeBSD.ORG Mon Dec 17 23:52:58 2007 Return-Path: Delivered-To: cvs-all@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 812C116A417; Mon, 17 Dec 2007 23:52:58 +0000 (UTC) (envelope-from phk@critter.freebsd.dk) Received: from phk.freebsd.dk (phk.freebsd.dk [130.225.244.222]) by mx1.freebsd.org (Postfix) with ESMTP id 476AA13C459; Mon, 17 Dec 2007 23:52:58 +0000 (UTC) (envelope-from phk@critter.freebsd.dk) Received: from critter.freebsd.dk (unknown [192.168.61.3]) by phk.freebsd.dk (Postfix) with ESMTP id C5DC017105; Mon, 17 Dec 2007 23:52:56 +0000 (UTC) Received: from critter.freebsd.dk (localhost [127.0.0.1]) by critter.freebsd.dk (8.14.2/8.14.2) with ESMTP id lBHNqt2h012992; Mon, 17 Dec 2007 23:52:56 GMT (envelope-from phk@critter.freebsd.dk) To: "M. Warner Losh" From: "Poul-Henning Kamp" In-Reply-To: Your message of "Mon, 17 Dec 2007 09:19:01 MST." <20071217.091901.627251640.imp@bsdimp.com> Date: Mon, 17 Dec 2007 23:52:55 +0000 Message-ID: <12991.1197935575@critter.freebsd.dk> Sender: phk@critter.freebsd.dk Cc: cvs-src@FreeBSD.org, bms@incunabulum.net, bms@FreeBSD.org, cvs-all@FreeBSD.org, src-committers@FreeBSD.org Subject: Re: cvs commit: src/sbin/atacontrol atacontrol.c X-BeenThere: cvs-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: CVS commit messages for the entire tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 17 Dec 2007 23:52:58 -0000 In message <20071217.091901.627251640.imp@bsdimp.com>, "M. Warner Losh" writes: >In message: <11419.1197903331@critter.freebsd.dk> > "Poul-Henning Kamp" writes: >: > * NAND Flash devices should not have their sectors erased unless >: >absolutely necessary, to implement wear levelling. >: >: Wrong, almost exactly the opposite in fact: >: >: Flash devices using wear-levelling should have data erased as soon as >: possible to give the wear-levelling the maximum amount of information >: and available space to work with. > >The formula for flash life has two components: The percentage of space >available and the data rate. So the more space, the longer it will >last for a given rate. It is actually quite a bit more complex than that, but for people who don't have access to the actual FAL algorithm, it is a useful first approximation. For some of the non-patented, practically unused FAL algorithms, it is even the strict truth. For NDA reasons, I can't go into too much details, there is a couple of very read-worth patents which M-Systems got and SanDisk bought with the company, which they are now sueing everybody and their aunt for infringing. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.