Comment 3 for bug 881465

I had experienced something similar in 11.04 when attempting to install grub on a RAID 1 /boot partition. My resolution was to partition like this:

sda

1GB sda1 - '/boot' ext2 | 100GB sda2(md0 - ext4) '/' | max sda3(md1 - ext4) '/array1'

sdb

1GB sdb1 - not mounted, ext2 | 100GB sdb2(md0 - ext4) '/' | max sdb3(md1 - ext4) '/array1'

To the best of my knowledge, this is a problem with GRUB2(I'm pretty sure there are existing bugs filed for this). The unfortunate side effect of this is that /boot is not redundant, but it only takes a few minutes to reinstall grub on another free partition, like sdb1 if sda fails. I wound up leaving a spare 1GB partition at the beginning of every disk in that machine for that reason.

I'll be trying something similar on a new box with Ubuntu 11.10 in the next few days, I'll post back my results.