how do you make sure that EVERY FILE in each copy is good.
Checksums.
Personally, I use TeraCopy to safely copy a folder/file from my main drive to my backups (there’s even an option on there that will save a checksum of said folder/file on the backup so that I can later run that checksum and see if anything has corrupted).
What do I do if there’s corruption? Simply delete the corrupted files and replace them with good copies from other backups.
Checksums.
Personally, I use TeraCopy to safely copy a folder/file from my main drive to my backups (there’s even an option on there that will save a checksum of said folder/file on the backup so that I can later run that checksum and see if anything has corrupted).
What do I do if there’s corruption? Simply delete the corrupted files and replace them with good copies from other backups.