I have(?) a 1T external drive I was using for backup (I use good old xcopy) of my Library.
One day the copy crashed with a drive fault. I restarted (the PC locked up), and I can still read anything on the drive EXCEPT that Library folder (causes another lockup). Win or Linux can not fix the drive (and Linux even locks when accessing that disk area)
Flash drives also hard fail without notice
Multiple copies
One of them should be offsite (and high ground and not in a forest or near a volcano)