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: Tue, 28 Apr 2009 17:28:22 -0700 Message-ID: <49F79F26.9060309@zytor.com> References: <1240574900.4507.2076.camel@ezra> <87hc0axhg9.fsf@frosties.localdomain> <49F68CE0.2010906@zytor.com> <1240957153.18303.689.camel@ezra> <18935.35747.471257.202356@notabene.brown> <49F78F26.2040909@zytor.com> <1240963225.18303.858.camel@ezra> <49F7997C.2070808@zytor.com> <1240964410.18303.895.camel@ezra> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1240964410.18303.895.camel@ezra> Sender: linux-raid-owner@vger.kernel.org To: Daniel Reurich Cc: Neil Brown , Dan Williams , Goswin von Brederlow , linux-raid@vger.kernel.org List-Id: linux-raid.ids Daniel Reurich wrote: >>> >> Grub is capable of doing that IF THE FIRMWARE CAN REACH IT. > > Well if the firmware can't find one if the disks, then it doesn't matter > what scheme we have. Even a single disk won't work. It is *quite* common that firmware can reach a subset of the disks. If not when the system is set up, then when a controller is blown and the user has to install a new one. I have seen this particular malfunction up close more times than I can count. > What's your beef. MD already reserve some space for the superblock, and > write-intent bitmap (which I believe is also replicated across the > member disks), so why not add some space to this to make it possible for > a bootloader as well. My beef is that you're actively promoting an extremely dangerous concept, dangerous exactly because it is seductive -- "it seems so easy." Most users, you included, apparently, typically will have no notion of the failure modes, and will pick the "easy" option. Booting is ugly business. I have dealt with the subtleties for almost two decades, and it riles me when people go and foist off bad ideas on users. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.