From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: md extension to support booting from raid whole disks. Date: Fri, 15 May 2009 09:13:30 -0700 Message-ID: <4A0D94AA.8020803@zytor.com> References: <20090503013342770.VMBT19475@cdptpa-omta01.mail.rr.com> <1241406283.17240.26.camel@ezra> <87fxff462s.fsf@frosties.localdomain> <21cdc7a16fbdd42979d52331db97c737.squirrel@neil.brown.name> <87ws8r2pqf.fsf@frosties.localdomain> <18953.2936.212863.158003@notabene.brown> <1242157469.18958.13.camel@ezra> <18954.43834.53155.793587@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <18954.43834.53155.793587@notabene.brown> Sender: linux-raid-owner@vger.kernel.org To: Neil Brown Cc: Daniel Reurich , Goswin von Brederlow , Linux RAID List-Id: linux-raid.ids Neil Brown wrote: > > Having a replicated boot loader and having a raid1 are conceptually > quite different things. > A raid1 says "keep N (typically 2) copies of the data somewhere for > me". > A replicated boot loader says "store this boot loader on every > bootable device". > One is more abstract, the other is more concrete. > > Maybe it is a very subtle distinction, but I think it is worth > maintaining. Get your boot-loader-installer to install at the front > of every drive - don't bother having a raid1 there that is never read > and hardly ever written.. > I think it is an unfortunate distinction (although I see why you want to make it), and one which goes in the wrong direction. As I've stated many times (and not just in this debate), I believe using the RAID-1 mechanism to replicate /boot across the entire span of devices is the right thing to do. Not just the boot loader, but all of /boot. Once you do that, you do want to write it on a regular basis, and using the RAID-1 code is the obvious way to do it. You can argue that it is an accidental effect of the way the current Linux RAID-1 code does it, but it's nevertheless extremely useful, widely deployed, and extremely resilient. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.