(there's a undetectable fault error rate, something along the lines of 1 in 10^20 bytes read or so will have an undetected error)
I just want to call this out because it's so important. That number, 10^20, sounds big, but considering the size of modern drives it's really not.
Randomly picking the WD 8TB Red NAS drive (WD60EFRX), which is designed for consume RAID as an example:
The spec sheet says the URE (unrecoverable read error) rate is at worst 1 x 10^14 per bits read. However, that drive holds 8 x 10^12 bytes! If you were to read every single byte there is about a 64% chance that at least 1 bit is read incorrectly.
(8 x 8 (bits per byte) x 10^12) / (1 x 10^14) = 64,000,000,000,000 / 100,000,000,000,000 = 0.64
Correct my math if I'm wrong, but this should make anyone think twice about using any kind of RAID as a "backup" solution. If you have a disk fail you have a better than 50/50 chance of introducing corrupt data during the rebuild process!
Frankly, ZFS-style checksumming is the future of files systems. It has to be for any data you care about.