[lotharcable2]

Mirrored raid is good. Other raid levels are of dubious value nowadays.

Ideally you use "software raid" or file system with the capabilities do scrubbing and repair to detect bitrot. Or have some sort of hardware solution that can do the same and notify the OS of the error correction.

And, as always, Raid-type solutions mostly exist to improve availability.

Backups are something else entirely. Nothing beats having lots of copies in different places.