Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263901AbUCZBEW (ORCPT ); Thu, 25 Mar 2004 20:04:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263861AbUCZAbr (ORCPT ); Thu, 25 Mar 2004 19:31:47 -0500 Received: from aslan.scsiguy.com ([63.229.232.106]:25104 "EHLO aslan.scsiguy.com") by vger.kernel.org with ESMTP id S263860AbUCZALN (ORCPT ); Thu, 25 Mar 2004 19:11:13 -0500 Date: Thu, 25 Mar 2004 17:10:24 -0700 From: "Justin T. Gibbs" Reply-To: "Justin T. Gibbs" To: Jeff Garzik cc: linux-kernel@vger.kernel.org, Kevin Corry , Neil Brown , linux-raid@vger.kernel.org Subject: Re: "Enhanced" MD code avaible for review Message-ID: <1048370000.1080259823@aslan.btc.adaptec.com> In-Reply-To: <406372C5.600@pobox.com> References: <760890000.1079727553@aslan.btc.adaptec.com> <16480.61927.863086.637055@notabene.cse.unsw.edu.au> <40624235.30108@pobox.com> <200403251200.35199.kevcorry@us.ibm.com> <40632804.1020101@pobox.com> <40632994.7080504@pobox.com> <1035780000.1080258411@aslan.btc.adaptec.com> <406372C5.600@pobox.com> X-Mailer: Mulberry/3.1.1 (Linux/x86) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1299 Lines: 29 >> None of the solutions being talked about perform "failing over" in >> userland. The RAID transforms which perform this operation are kernel >> resident in DM, MD, and EMD. Perhaps you are talking about spare >> activation and rebuild? > > This is precisely why I sent the second email, and made the qualification > I did :) > > For a "do it in userland" solution, an initrd or initramfs piece examines > the system configuration, and assembles physical disks into RAID arrays > based on the information it finds. I was mainly implying that an initrd > solution would have to provide some primitive failover initially, before > the kernel is bootstrapped... much like a bootloader that supports booting > off a RAID1 array would need to do. "Failover" (i.e. redirecting a read to a viable member) will not occur via userland at all. The initrd solution just has to present all available members to the kernel interface performing the RAID transform. There is no need for "special failover handling" during bootstrap in either case. -- Justin - 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/