I have two 2TB disks. I am installing Ubuntu 12.04 using the alternate version of the server cd. On the partitioning page I have done my partitioning as follows

/dev/sda1 - 32 MB - bios_grub
/dev/sda2 - 50 GB -raid device
/dev/sda3 - 8 GB -raid device
/dev/sda4 - Balance full GB - raid device

/dev/sdb1 - 32 MB - bios_grub
/dev/sdb2 - 50 GB -raid device
/dev/sdb3 - 8 GB -raid device
/dev/sdb4 - Balance full GB - raid device

After this I have setup raid devices
/dev/md0 for /(/dev/sda2 + /dev/sdb2) for / ext4
/dev/md1 for swap( /dev/sda3 + /dev/sdb3)for swap
/dev/md2 for /home(/dev/sda4 + /dev/sdb4)for /home ext4

The installation finishes it shows that it is installing grub to /dev/sda and /dev/sdb. But once the system reboots it falls into grub rescue> mode. on doing ls I can not see the md devices only hd once.

I also tried booting into rescue mode with the install cd and doing grub-install /dev/sda and /dev/sdb. What am I doing wrong ? Why is grub2 not detecting the raid revices ?

UPDATE: I just did the same steps with Ubuntu 10.04 and it worked perfectly fine. I wiped out the RAID and partitions and everything and did it from scratch. I think the issue is with Ubuntu 12.04 and the way it partitions 2 TB disks