In the previous post I said that you cannot boot from the software RAID array. In fact, this is not true. All the widespread bootloaders, from Windows NT, Linux LILO, and GRUB, would successfully load OS from a RAID 1 (mirror volume).
It should be noted that some further actions must be undertaken for RAID 1 boot volume when you plan to build a RAID.
Since the mirroring technique does not extend to the Master Boot Record (MBR), you must copy the MBR manually between drives in a software mirror. Otherwise, once the primary (boot) drive fails, you will end up with an unbootable system.
Surely, there will be no irreversible data loss - all you need is to just mount the disk into some other machine and read it, but you get no automatic recovery in case the disk fails in operation, requiring a reboot.
