Step 1 is a FULL backup of what you have now to an external disk.
Allow me to just cut paste
Concatenation or spanning of drives is not one of the numbered RAID levels, but it is a popular method for combining multiple physical disk drives into a single logical disk . It provides no data redundancy. Drives are merely concatenated together, end to beginning, so they appear to be a single large disk
I read this when i was thinking about doing almost the same - but ended up doing a mirror raid.
