From owner-freebsd-hackers@FreeBSD.ORG Mon Aug 22 07:00:37 2005 Return-Path: X-Original-To: freebsd-hackers@freebsd.org Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 779A816A431 for ; Mon, 22 Aug 2005 07:00:37 +0000 (GMT) (envelope-from imp@bsdimp.com) Received: from harmony.village.org (vc4-2-0-87.dsl.netrack.net [199.45.160.85]) by mx1.FreeBSD.org (Postfix) with ESMTP id AD56B43D70 for ; Mon, 22 Aug 2005 07:00:22 +0000 (GMT) (envelope-from imp@bsdimp.com) Received: from localhost (localhost.village.org [127.0.0.1]) by harmony.village.org (8.13.3/8.13.3) with ESMTP id j7M6vh43041622; Mon, 22 Aug 2005 00:57:48 -0600 (MDT) (envelope-from imp@bsdimp.com) Date: Mon, 22 Aug 2005 00:57:50 -0600 (MDT) Message-Id: <20050822.005750.56564930.imp@bsdimp.com> To: hselasky@c2i.net From: "M. Warner Losh" In-Reply-To: <200508210235.17608.hselasky@c2i.net> References: <200508201230.37976.hselasky@c2i.net> <20050820.171238.122195775.imp@bsdimp.com> <200508210235.17608.hselasky@c2i.net> X-Mailer: Mew version 3.3 on Emacs 21.3 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-2.0 (harmony.village.org [127.0.0.1]); Mon, 22 Aug 2005 00:57:48 -0600 (MDT) Cc: freebsd-hackers@freebsd.org Subject: Re: Parking disk drive heads X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 22 Aug 2005 07:00:37 -0000 In message: <200508210235.17608.hselasky@c2i.net> Hans Petter Selasky writes: : On Sunday 21 August 2005 01:12, M. Warner Losh wrote: : > In message: <200508201230.37976.hselasky@c2i.net> : > : > Hans Petter Selasky writes: : > : On Saturday 20 August 2005 10:18, Mike Silbersack wrote: : > : > On Fri, 19 Aug 2005, Doug Ambrisko wrote: : > : > > Flash is nice but it has some issues. Atleast dropping it isn't one! : > : > > : > : > > Doug A. : > : > : > : > I'd be really happy if I could get a USB flash drive to last more than : > : > 8 months. Luckily, I started weekly backups after the first failure. : > : > That helped a lot when the second failure happened. : > : : > : Flash drives does usually not last more than 10000 writes, per bit, from : > : what I know. Probably you need some kind of special file-system that : > : moves the files around as the write quoute gets used up! Eventually the : > : size of the disk will reach zero, and you have to move the files : > : elsewhere :-) But this is probably off topic. : > : > Actually, 10,000 writes per bit is one or two orders of magnitude too : > low these days. It was more typical for the Linear Flash PCMCIA cards : > from 10 years ago. Today, typically flash devices are good for more : > like 100,000 or 500,000 writes per cell, and all the fobs you'd buy : > these days have built-in wear averaging. I've tried three times now : > to wear out a flash by writing an incrementing counter to a single : > location only to give up after weeks of hammering due to external : > factors (power failure, network failure, etc). : : Are you sure that the flash drive is not caching the writes in RAM? Yes. I'm 100% positive. These devices do not have RAM. Warner