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I've installed Ubuntu 12.04.1 in a new server and set up the 4 hard drives with 3 RAID 1 devices, the configuration is such that the first two drives have md0 (swap space) and md1 (/) with the third and fourth drives having md2 (/var).

I've been testing the operation under a drive failure and found that the system boots fine if I remove disk two but if I remove disk one then the system gets to grub and then just restarts. I'm confused as to why grub appears to be loading properly from disk two but then the boot fails.

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It is normal behavior, when you install grub on the second disk, when the first disk is present too. In case if the first disk is removed, the second disk became as the first, but in the grub config it has to find other boot files on the second drive, which have not this files.

You have to copy MBR from first disk to the second:

dd if=/dev/sda of=/dev/sdb bs=512 count=1

MBR of the first and second disk has to be identical...

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I've tried this and with the first drive removed it still won't go past the grub menu and just reboots. Any more thoughts? – beacon_bonanza Aug 31 '12 at 8:59
When the grub menu appears it looks fine, then the system just restarts. – beacon_bonanza Sep 3 '12 at 8:19

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