From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hari Bhaskaran Subject: Re: s/w raid and bios renumbering HDs Date: Mon, 31 Oct 2005 15:59:38 -0800 Message-ID: <4366AFEA.6030906@gmail.com> References: <8d03025a0510310756q7410ef13v6ffb4764229b2eb6@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: dean gaudet Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids on 10/31/2005 11:47 AM dean gaudet said the following: > huh i wonder if the bios has tweaked the ide controller to swap the > primary/secondary somehow -- probably cuts down on support calls for > people who plug things in wrong. there could be a bios option to stop > this swapping. > Not that I can see. Cheap dell machines like the one I have come with a single-page bios setup screen. However, now I think it may not all be the bios. I have two more HDs connected with an Adaptec pci-ide controller (which I plan to use for a raid-5). I will do some more experiments so that I understand how this whole thing works. > for raids other than the root raid you pretty much want to edit > /etc/mdadm/mdadm.conf and make sure it has "DEVICE partitions" and has > So that "DEVICE paritions" line was really supposed to be there? Hehe... I thought it was just a help message and replaced it with "DEVICE /dev/hda1 /dev/hdc1" :) > ARRAY entries for each of your arrays listing the UUID. you can generate > these entries with "mdadm --detail --scan" (see examples on man page). > it took me a whole Sunday to figure that one out. I followed the howto, created the array and didn't know how to start it back up after a reboot ( I hadn't asked mdadm to start raid devices at system startup). Even when I did that, the array didn't come up until I put those ARRAY lines. I kept on editing raidtab - I hadn't read the tiny print in mdadm manpage. If I ever end up in a situation with a non-root raid down (say I did --stop), how do I start it back up? (--run seems to give me some errors). Anyways, more "rtfm" to do. > you can plug the non-root disks in any way you want and things will still > work if you've configured this. > That is nice. > the root is the only one which you need to be careful with -- when debian > installs your kernel it constructs an initrd which lists the minimum > places it will search for the root raid components... for example on one > of my boxes: > > # mkdir /mnt/cramfs > # mount -o ro,loop /boot/initrd.img-2.6.13-1-686-smp /mnt/cramfs > # cat /mnt/cramfs/script > ROOT=/dev/md3 > mdadm -A /dev/md3 -R -u 2b3a5b77:c7b4ab81:a2b8322a:db5c4e88 /dev/sdb4 /dev/sda4 > # umount /mnt/cramfs > Did u install yours with raid options in the debian installer? I dont think my initrd image would have all these ( I dont have access to the machine now to check) - but I wouldn't think the mkinitrd that I used to created the initrd image would know that I am using raid or not ( I am talking about the mdadm references in your script). Or are you saying you added these yourself? > it's only expecting to look for the root raid components in those two > partitions... seems kind of unfortunate really 'cause the script could > be configured to look in any partition. > > in theory you can hand-edit the initrd if you plan to move root disks to > another position... you can't mount a cramfs rw, so you need to mount, > copy, edit, and run mkcramfs ... and i suggest not deleting your original > initrd, and i suggest copy&pasting the /boot/grub/menu.lst entries to give > you the option of booting the old initrd or your new made-by-hand one. > > > >> title Debian GNU/Linux, kernel 2.6.13.3-vs2.1.0-rc4-RAID-hda >> root (hd0,0) >> kernel /boot/vmlinuz-2.6.13.3-vs2.1.0-rc4 root=/dev/md0 ro >> initrd /boot/initrd.img-2.6.13.3-vs2.1.0-rc4.md0 >> savedefault >> boot >> >> title Debian GNU/Linux, kernel 2.6.13.3-vs2.1.0-rc4-RAID-hdc >> root (hd1,0) >> kernel /boot/vmlinuz-2.6.13.3-vs2.1.0-rc4 root=/dev/md0 ro >> initrd /boot/initrd.img-2.6.13.3-vs2.1.0-rc4.md0 >> savedefault >> boot >> > > i don't think you need both. when your first disk is dead the bios > shifts the second disk forward... and hd0 / hd1 refer to bios ordering. > i don't have both in my configs, but then i haven't bothered testing > booting off the second disk in a long time. (i always have live-cds > such as knoppix handy for fixing boot problems.) > > -dean > > -- Hari