> What would happen if one of the RAID arrays failed (e.g. two
drives die
> in RAID 5 array 1)? Would the data be safe, would I lose all data, or
> would I just lose the data that was on the failed array?
Two drives in either RAID will most likely kill your LVM.
If you need two drive reliability you need RAID6 or depending on the
tradeoffs you want to make RAID 5 + hot spare.
For performance you want RAID 1 + 0 (possibly + hot spares)