I just set up Ubuntu 12.04.3 Server LTS with software RAID 10. Here's the steps I followed for setting up RAID:
1) Automatically partition one of the drives in order to determine the sizes of the partitions to create. In my case the suggested layout was: 1.0 MB free space 98.6 MB B EFIboot 983.0 GB ext4 / 17.1 GB swap
2) Change the / and swap partitions to: use for "Physical volume for RAID". Ubuntu wouldn't allow me to select a RAID partition as bootable, so the EFIboot partition can stay as-is.
3) Partition the other 3 disks with exactly the same partition layout. I decided to leave 99.6 MB of free space at the beginning of each drive, so that there is a direct match between the four drives. (So there are 98.6 MB unused partitions on each of the four drives).
4) Set up the RAID volumes. Note: I couldn't delete an existing RAID volume because it was being used as swap. I ran this at the terminal: swapoff /dev/md127 http://mikebeach.org/2013/10/25/cannot-delete-a-raid-swap-partition-during-ubuntu-installation/
5) Select the RAID volumes, and use rd0 and rd1 for / and swap
The system installed fine OK on the RAID / partition, but when it rebooted GRUB just sits there at the grub> prompt. Typing
boot gives: "error: no loaded kernel.".