He thinks everything is fine, but unless he has some way to verify the data he copied from that failing drive there may be corrupted data that he will notice la

He thinks everything is fine, but unless he has some way to verify the data he copied from that failing drive there may be corrupted data that he will notice later. I really wish Apple would add a filesystem with some data integrity features. Even if they're not going to go with ZFS they could at least have a checksum so that you can know when your data is bad even if it can't be repaired.