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Re: Software Raid On Boot

Rejean Proulx wrote:
Does software raid work on a boot device? If not, that could be one of my problems. If it does, should grub contain md0?

You can mirror (RAID1) the boot device, but you cannot stripe (RAID0) it.
Grub needs to boot from the "raw" /dev/hda etc. device, it knows nothing about software RAID.

This is the grub.conf from a (RHEL AS4) system I setup yesterday with RAID1 partitions for / and /boot:

title Red Hat Enterprise Linux AS (2.6.9-11.ELsmp)
        root (hd0,0)
        kernel /vmlinuz-2.6.9-11.ELsmp ro root=/dev/md1 rhgb quiet
        initrd /initrd-2.6.9-11.ELsmp.img

/boot is /dev/md0, which comprises /dev/hda1 and /dev/hdd1. / is /dev/md1 which comprises /dev/hda3 and /dev/hdd3. GRUB must be installed into the MBR of /dev/hda (for some strange reason I had to do this manually on this install). GRUB doesn't handle RAID1 all than well, lilo does it better as it understands RAID1 and installs the correct MBR on each disk. GRUB is not able to boot from /dev/hdd1; if /dev/hda fails I will have to either modify /boot/grub/grub.conf and install GRUB in /dev/hdd, or move the disk so it becomes /dev/hda. Because of the way lilo works it can install boot sectors on /dev/hda and /dev/hdd, both of which will work.

Nigel Wade, System Administrator, Space Plasma Physics Group,
            University of Leicester, Leicester, LE1 7RH, UK
E-mail :    nmw ion le ac uk
Phone :     +44 (0)116 2523548, Fax : +44 (0)116 2523555

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