From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: "Enhanced" MD code avaible for review Date: Thu, 25 Mar 2004 19:14:59 -0500 Sender: linux-raid-owner@vger.kernel.org Message-ID: <40637603.10902@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> <1048370000.1080259823@aslan.btc.adaptec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1048370000.1080259823@aslan.btc.adaptec.com> To: "Justin T. Gibbs" Cc: linux-kernel@vger.kernel.org, Kevin Corry , Neil Brown , linux-raid@vger.kernel.org List-Id: linux-raid.ids Justin T. Gibbs wrote: >>>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. hmmm, yeah, agreed. Jeff