question about mdadm + grub interaction
Greetings. In order to insure that a Debian stock kernel (i.e. the
kernel installed from the linux-image-2.6.22-2-686-bigmem package) boots
correctly off of a mdadm RAID 1 set of two disks if one of the disks is
dead, do we:
1) Have to manually install grub on the MBR on *both* drives, or is this
done automagically by the grub package installer if the RAID 1 set
is in place at the time of the grub install?
2) Need to have something that looks like this in /boot/grub/menu.lst:
A)
title Debian GNU/Linux, kernel 2.6.21-2-686-bigmem, RAID1
root (hd0,0)
kernel /vmlinuz-2.6.21-2-686-bigmem root=/dev/md2 md=0,/dev/sda1,/dev/sdb1 ro
initrd /initrd.img-2.6.21-2-686-bigmem
savedefault
title Debian GNU/Linux, kernel 2.6.21-2-686-bigmem, BROKEN RAID1
root (hd0,0)
kernel /vmlinuz-2.6.21-2-686-bigmem root=/dev/md2 md=0,/dev/sdb1 ro
initrd /initrd.img-2.6.21-2-686-bigmem
savedefault
i.e. with the 'md=...' configuration options? Or do we just need this:
B)
title Debian GNU/Linux, kernel 2.6.21-2-686-bigmem
root (hd0,0)
kernel /vmlinuz-2.6.21-2-686-bigmem root=/dev/md2 ro
initrd /initrd.img-2.6.21-2-686-bigmem
savedefault
which is the sort of thing that is installed automagically by the
kernel package installer?
3) Need to have the 'md=...' configuration option point at the *boot*
partition, or the *root* partition, so that if we have:
md0 : active raid1 sda1[0] sdb1[1]
md2 : active raid1 sda3[0] sdb3[1]
and
/dev/md0 /boot
/dev/md2 /
do we then need:
md=0,/dev/sda1,/dev/sdb1
md=0,/dev/sdb1
or:
md=2,/dev/sda3,/dev/sdb3
md=2,/dev/sdb3
Any pointers to *detailed* documentation about how the 'md=...' option
works would be much appreciated; I've already seen:
http://www.debian-administration.org/articles/238
(which has a question at the very bottom of the page, a bit over two
months old, asking very similar sorts of questions -- no answer on the
page so far...); and
http://alephnull.net/software/linux-raid/4%20-%20Setup.html
(which is lilo-specific, but also informative); and
http://www.epimetrics.com/topics/one-page?page_id=449&topic=Bit-head%20Stuff&page_topic_id=120
AND:
http://www.opensubscriber.com/message/linux-raid@vger.kernel.org/7889881.html
(which is informative, but doesn't get at precise answers to my questions).
Thanks much,
--
Steve Lane
System, Network and Security Administrator
Doudna Lab
Biomolecular Structure and Mechanism Group
UC Berkeley
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