That's what RAID-5 (and variants) are. Btrfs (and maybe ZFS?) support making certain files or volumes use parity stripes so corruption is recoverable in-place.

That's what RAID-5 (and variants) are. Btrfs (and maybe ZFS?) support making certain files or volumes use parity stripes so corruption is recoverable in-place. Per Shannon, these things are all related. You can think of error-correcting codes as a form of replica compression: get the reliability of multiple replicas at a fraction of the size. Like compression, there are CPU-time tradeoffs as well. Writing two replicas can happen completely in parallel (they're independent) and it imposes basically no CPU cost. Writing an error-correcting code imposes a CPU penalty and for files that get mutated they impose write overhead (though SSDs have that anyway making it less of a concern). I think a lot of people assume bitrot happens over time and you need backups anyway, so why take the hit on the primary for some small protection? The reasonableness of that depends on your specific use case and risk tolerance.