- There is no way to create a RAID volume from an existing disk. You have to create a new volume from scratch and re-image.
- There seem to be a need to special drivers. When I boot up Linux with the RAID volume defined it still shows 2 disks!
- Does the controller (or controlling software) verifies the write? If it doesn't and an error is discovered at read time it is too late.
- If you have a corrupted file due to a software glitch for example you still need a backup. Otherwise you have a mirror of corrupted files.
- If the motherboard dies can we take the disks and boot up from another computer with potentially a different chipset - RAID or regular?
Due to the above questions and issues I ended up using the secondary disk for backups.