I'm using Ubuntu 12.04 LTS (Precise Pangolin) with grub 1.99. I installed on a RAID10 multidevice BTRFS partition. I thought that multidevice support is included in grub for a while but on boot I'm dropped to a initramfs shell, because it fails to mount root ("invalid argument"). This is actually the same message I get if I want to mount a btrfs volume without executing btrfs device scan. Therefore I wonder: Does Ubuntu's grub version even support boot from btrfs mutlidevice ?