From owner-freebsd-hackers@FreeBSD.ORG Thu Mar 5 21:45:40 2009 Return-Path: Delivered-To: freebsd-hackers@FreeBSD.ORG Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 9145B1065670 for ; Thu, 5 Mar 2009 21:45:40 +0000 (UTC) (envelope-from dthiele@gmx.net) Received: from mail.gmx.net (mail.gmx.net [213.165.64.20]) by mx1.freebsd.org (Postfix) with SMTP id DFFBE8FC1E for ; Thu, 5 Mar 2009 21:45:39 +0000 (UTC) (envelope-from dthiele@gmx.net) Received: (qmail invoked by alias); 05 Mar 2009 21:45:37 -0000 Received: from p54863FC3.dip.t-dialin.net (EHLO impala.vnws.lan) [84.134.63.195] by mail.gmx.net (mp065) with SMTP; 05 Mar 2009 22:45:37 +0100 X-Authenticated: #19302822 X-Provags-ID: V01U2FsdGVkX18Eclx8lMwE3jNnyDZc0HWH4ZFUo3fiWkkUJgQzts k64kVqwFbkXSSZ Message-ID: <49B0480A.3090909@gmx.net> Date: Thu, 05 Mar 2009 22:45:46 +0100 From: Daniel Thiele User-Agent: Thunderbird 2.0.0.19 (X11/20090124) MIME-Version: 1.0 To: Ed Schouten References: <200903041938.n24Jcqdr060153@lurza.secnetix.de> <49AF1C1B.3050604@gmx.net> <49AF9381.50709@FreeBSD.org> <49B04281.2030406@gmx.net> <20090305212807.GC19161@hoeg.nl> In-Reply-To: <20090305212807.GC19161@hoeg.nl> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 X-FuHaFi: 0.49 Cc: octavian.covalschi@gmail.com, freebsd-hackers@FreeBSD.ORG, Alexander Motin Subject: Re: Spin down HDD after disk sync or before power off 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: Thu, 05 Mar 2009 21:45:40 -0000 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Ed Schouten wrote: | * Daniel Thiele wrote: |> Looking at the numbers in the Hitachi drive specifications Tobias an I |> dug out from the Hitachi website (see replies in the Joerg Sonnenberger |> branch of this thread) the normal Load/Unload count is about 30 times |> higher than the Emergency Unload count. | | Have you also looked at the definition of `emergency unload'? Maybe this | number doesn't actually refer to the number of unloads caused by power | loss, but because they detect a very high amount of vibration. But I'm | not a hard disk expert. | I am no disk expert either. The Hitachi TravelStar 5K320 specification says on this topic: 6.3.6.1 Emergency unload When hard disk drive power is interrupted while the heads are still loaded the micro code cannot operate and the normal 5 -volt power is unavailable to unload the heads. In this case, normal unload is not possible. The heads are unloaded by routing the back EMF of the spinning motor to the voice coil. The actuator velocity is greater than the normal case and the unload process is inherently less controllable without a normal seek current profile. Emergency unload is intended to be invoked in rare situations. Because this operation is inherently uncontrolled, it is more mechanically stressful than a normal unload. So it seems to be a kind of self protection mechanism that electro-mechanically tries to get the heads in a save position without firmware or microcode intervention in the case of a sudden power outage. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.11 (FreeBSD) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAkmwSAIACgkQCOZKcWNoXg7vlQCgzcSvK25cLBfemmsC7/xXmtcl /7kAmwQGM5xFVjZJW7YGqNWaWIXuXqcu =cPcz -----END PGP SIGNATURE-----