From owner-freebsd-questions@FreeBSD.ORG Wed Jun 24 09:44:42 2009 Return-Path: Delivered-To: FreeBSD-Questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3790C1065672 for ; Wed, 24 Jun 2009 09:44:42 +0000 (UTC) (envelope-from wojtek@wojtek.tensor.gdynia.pl) Received: from wojtek.tensor.gdynia.pl (wojtek.tensor.gdynia.pl [IPv6:2001:4070:101:2::2]) by mx1.freebsd.org (Postfix) with ESMTP id 324238FC1C for ; Wed, 24 Jun 2009 09:44:40 +0000 (UTC) (envelope-from wojtek@wojtek.tensor.gdynia.pl) Received: from wojtek.tensor.gdynia.pl (localhost [IPv6:::1]) by wojtek.tensor.gdynia.pl (8.14.3/8.14.3) with ESMTP id n5O9iYCV063561; Wed, 24 Jun 2009 11:44:35 +0200 (CEST) (envelope-from wojtek@wojtek.tensor.gdynia.pl) Received: from localhost (wojtek@localhost) by wojtek.tensor.gdynia.pl (8.14.3/8.14.3/Submit) with ESMTP id n5O9iY4V063558; Wed, 24 Jun 2009 11:44:34 +0200 (CEST) (envelope-from wojtek@wojtek.tensor.gdynia.pl) Date: Wed, 24 Jun 2009 11:44:34 +0200 (CEST) From: Wojciech Puchar To: freebsd@t41t.com In-Reply-To: <20090624093223.GF3468@ece.pdx.edu> Message-ID: References: <20090622230729.GA20167@thought.org> <20090623201041.GA23561@thought.org> <20090623205944.GA43982@Grumpy.DynDNS.org> <20090624010922.GA24335@thought.org> <20090624093223.GF3468@ece.pdx.edu> User-Agent: Alpine 2.00 (BSF 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: FreeBSD-Questions@freebsd.org Subject: Re: you're not going to believe this. X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 24 Jun 2009 09:44:42 -0000 > First, be careful about statements like "10 years before it fails to hold > state." Usually that means if you write data to the device and put it on a > shelf, you've got 10 years before the data is unreadable. Being marketing possibly it's true if you will write it few times and no more ;) store it in perfect stable room temperature with low natural radiation background etc. > for a decade? The number you probably care about is how long _in active > use_ the drive will last, and that's probably _not_ 10 years. The primary 10000 writes of it's size if it would be properly managed (flash filesystem). As it emulates disk divide it by at least two on writing large files, at least 20 in case of random small writes. > is less noticeable. Implementing wear leveling in OS-level software > isn't feasible. As I mentioned, wear leveling happens within the chip, > so the OS doesn't even know a block swap has occurred. (As an extension you are wrong. flash chips doesn't do this. There is a controller that do this. If it would give simple interface to flash chips and say PCI-Express or SATA, making proper flash filesystem would be possible.