It seems that, since btrfs development began, various communities have touted both it and ZFS as inherently more advanced filesystems for preventing corruption, bit rot, etc.
What features of btrfs or ZFS make them so suitable for both the detection and repair of "bit rot"?
Can btrfs detect and repair bit rot with only a single physical HDD, or does it require multiple for redundancy? If the latter, why not use more stable and vanilla filesystems (like ext4 and friends) atop regular RAID configurations?