If your raid controller fails, it's hard to get data off a single mirrored drive with most manufacturers, and software raids, too. (Ask Bob*)
Actually, it was quite easy to mount one of my old mirror on a new box to get data off of the drive with Linux using md. The drive wasn't recognized automatically and I had to run some command or other but it was pretty straightforward.
Question: If you have an older version of the blockchain, would the blockchain file be synched when the node joins the network, or will it be downloaded again?
Question2: Doesn't a Lighning node need a local copy of the chain, too?
It get synched. It just takes a while to catch-up. Though if you have plenty of internal bandwidth and you're not in a hurry, you can just have your node synch from one of your other ones.
LN connects to a bitcoin node, surely?