Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758095AbXHRTVT (ORCPT ); Sat, 18 Aug 2007 15:21:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756941AbXHRTVG (ORCPT ); Sat, 18 Aug 2007 15:21:06 -0400 Received: from wx-out-0506.google.com ([66.249.82.236]:53623 "EHLO wx-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757269AbXHRTVE (ORCPT ); Sat, 18 Aug 2007 15:21:04 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=RLj9kGbNXZqehPCjp7DqH63/iu11+Z93tuYGA1q7UOTk1Pt3oWhVAPffuABGcfO3dzrbzk/D20gMJs2HiQxo078Pj49goSxWLDSL0/XCNm7qHIdsOvDePNPib6pIxYTKZPIfYtkc0fsffoXF2vkX0c5DXXo5s0zHfWolrwoiYg0= Message-ID: Date: Sat, 18 Aug 2007 11:21:02 -0800 From: "Brennan Ashton" To: "Jan Engelhardt" Subject: Re: power off disk drives while running Cc: "Marty Leisner" , linux-kernel@vger.kernel.org In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <200708181608.l7IG8Jmm006141@dell2.home> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2031 Lines: 47 On 8/18/07, Jan Engelhardt wrote: > > On Aug 18 2007 12:08, Marty Leisner wrote: > > > >In embedded system design, it may be useful to poweroff the disks (as opposed > >to merely spinning them down). We want to leave the system running while > >the disk is powered down, and let the disk powerup when it needs to be > >spun up. > > That means you also have to power it on... > > >While the "power off mechanism" would be platform dependent, is there a > >generic path to announce "prepare for power going away"? > > I do not see why that would be needed from a software point of view. Just make > sure that the disk does not needlessy emergency-park when pulling power. When > someone wants to write to disk, the request goes to the device driver, which > hands it to the controller, which hands it to the disk. And your controller > should be able to handle it (e.g. wait until reconnect) when there is a request > for a disk that is powered off. > > > Jan > -- > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > I see this a a very important feature in the embedded system relm, I have worked on two projects that required extreme power management, and massive data storage. The ability to fully turn off a drive while the system is running is key. It seems like this should be able to be done from a kernel point of view rather than extra hardware. Although if is not in the IDE/SATA spec then extra hardware would be necessary. -- Brennan Ashton Bellingham, Washington "The box said, 'Requires Windows 98 or better'. So I installed Linux" - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/