Date: Mon, 17 Dec 2007 23:52:55 +0000 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: "M. Warner Losh" <imp@bsdimp.com> 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 Message-ID: <12991.1197935575@critter.freebsd.dk> In-Reply-To: Your message of "Mon, 17 Dec 2007 09:19:01 MST." <20071217.091901.627251640.imp@bsdimp.com>
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In message <20071217.091901.627251640.imp@bsdimp.com>, "M. Warner Losh" writes: >In message: <11419.1197903331@critter.freebsd.dk> > "Poul-Henning Kamp" <phk@phk.freebsd.dk> 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.
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