From mboxrd@z Thu Jan 1 00:00:00 1970 From: Moshe Yudkowsky Subject: Yes, but please provide the clue (was Re: [PATCH] Use new sb type) Date: Tue, 29 Jan 2008 05:25:20 -0600 Message-ID: <479F0D20.20306@pobox.com> References: <479E1C95.1040008@dgreaves.com> <479E232E.1030801@rabbit.us> <479E2DDA.5040102@dgreaves.com> <479EA6DE.9070503@dionic.net> <479EF3C8.7010509@rabbit.us> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <479EF3C8.7010509@rabbit.us> Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids > * The only raid level providing unfettered access to the underlying > filesystem is RAID1 with a superblock at its end, and it has been common > wisdom for years that you need RAID1 boot partition in order to boot > anything at all. Ah. This shines light on my problem... > The problem is that these three points do not affect any other raid > level (as you can not boot from any of them in a reliable fashion > anyway). I saw a number of voices that backward compatibility must be > preserved. I don't see any need for that because: > > * The distro managers will definitely RTM and will adjust their flashy > GUIs to do the right thing by explicitly supplying -e 1.0 for boot devices The Debian stable distro won't let you create /boot on an LVM RAID1, but that seems to be the extent of current RAID awareness. Using the GUI, if you create a large RAID5 and attempt to boot off it -- well, you're toast, but you don't find out until LILO and grub portion of the installation fails. > * A clueless user might burn himself by making a single root on a single > raid1 device. But wait - he can burn himself the same way by making the > root a raid5 device and rebooting. Okay, but: > Why do we sacrifice "the right thing to do"? To eliminate the > possibility of someone shooting himself in the foot by not reading the > manual? Speaking for clueless users everywhere: I'd love to Read The Fine Manual, but the Fine md, mdadm, and mdadm.conf Manuals that I've read don't have information about grub/LILO issues. A hint such as "grub and LILO can only work from RAID 1 and superblocks greater than 1.0 will toast your system in any case" is crucial information to have. Not everyone will catch this particular thread -- they're going to RTFM and make a mistake *regardless*. And now, please excuse me while I RTFM to find out if I change the superblocks to 1.0 from 1.2 on a running array... -- Moshe Yudkowsky * moshe@pobox.com * www.pobox.com/~moshe "If you're not part of the solution, you're part of the process." -- Mark A. Johnson