Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756977AbXHRQVh (ORCPT ); Sat, 18 Aug 2007 12:21:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755581AbXHRQV3 (ORCPT ); Sat, 18 Aug 2007 12:21:29 -0400 Received: from sovereign.computergmbh.de ([85.214.69.204]:51328 "EHLO sovereign.computergmbh.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754868AbXHRQV2 (ORCPT ); Sat, 18 Aug 2007 12:21:28 -0400 Date: Sat, 18 Aug 2007 18:21:27 +0200 (CEST) From: Jan Engelhardt To: Marty Leisner cc: linux-kernel@vger.kernel.org Subject: Re: power off disk drives while running In-Reply-To: <200708181608.l7IG8Jmm006141@dell2.home> Message-ID: References: <200708181608.l7IG8Jmm006141@dell2.home> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1137 Lines: 28 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/