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
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