No, it doesn't work like that, backup is not redundancy. To detect a bad block you first need to read it, you can't just know when a file becomes corrupt. And r

No, it doesn't work like that, backup is not redundancy. To detect a bad block you first need to read it, you can't just know when a file becomes corrupt. And reading every block is very expensive and doesn't provide predictable guarantees. Instead proper backup has built in redundancy to account for lost blocks and so does proper data storage. Checksums are not visible to users in neither case. And backup has to be incremental to prevent disasters.