And the bad sectors are not dealt with by reformatting, because writing zeroes will result in reading zeroes successfully, promoting the bad sectors to good sectors.
I know I sound like a broken record... but, If you can pull the drive and run the manufacturer's diagnostics in a windows PC, it will...
1) Scan every single sector (extended drive test)
2) Report after scan and ask if you want to "fix" bad blocks (mark,relocate, and update error map)
3) Report if the threshold of "too many" bad sectors is reached and determine if the drive is considered a "failure"