A RAID drive isn’t a backup, but an appropriately configured RAID will prevent data loss should a single drive go bad.
I cannot imagine storing emails and other important data on anything less than a RAID - the exception being my WayBackMachine for my MAC, but then again I also have off-site storage
Yes but RAID only lets you recover from a drive failure in the moment. It’s of little use when you’re trying to restore data that was deleted or destroyed two years ago.