From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Tokarev Subject: Re: Booting from a raid1 device ? Date: Thu, 30 Oct 2003 03:54:48 +0300 Sender: linux-raid-owner@vger.kernel.org Message-ID: <3FA06158.9040007@tls.msk.ru> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: To: "Cress, Andrew R" Cc: donj@asaca.com, linux-raid@vger.kernel.org List-Id: linux-raid.ids Cress, Andrew R wrote: > Don, > > Yes, it certainly can be done. I do it all the time. > > It's not hard with lilo, but grub doesn't support raid/md boot devices > yet. This means that the grub boot record doesn't automatically get > written to the second disk. In short, choose lilo for root mirroring if > possible. Ugh-blah. Excuse me folks, but.. maybe someone will be able to answer this one: why the hell a boot loader should "mirror" anything to the second disk? :) That is. Place standard MBR into the boot sector. An MBR that will boot from active partition. Be it e.g. /dev/hda and /dev/hdb. Create raid1 device from /dev/hda1 and /dev/hdb1. Mark both partitions as active. And install whatever boot loader you want into /dev/md1 - it will be mirrored automatically to /dev/hda1 and /dev/hdb1 (and to whatever else disks you'll use). Should your first disk fail, the system will either not boot because of bios limitations, or bios may "remap" /dev/hdb into /dev/hda (to be 0x80), and in this case boot procedure will work. Well, ok, a boot loader should be able to determine real offsets from the start of the disk, not from the start of raid device. I don't know whenever grub can do that - lilo apparently does, as all our systems are set up exactly this way... /mjt