Wow... the numbers in this paper are surprising, to me, at least.

https://www.usenix.org/conference/fast-08/analysis-data-corruption-storage-s...

Note that this research was presented at FAST '08, seven (7) years ago. Anecdotal evidence suggests the situation hasn't gotten much better - BERs have stayed pretty steady over that time AFAIK, but the size of disks has gone up. That means the likelihood of problems on any given disk has gone *up*. Ouch.