The terms “bad sector” and “bad cluster” refer to a specific section of a digital storage device that has been rendered unusable for reading and writing data. When a computer says it has found bad sectors or clusters it means that it has identified part of a connected storage medium that it can’t access. The computer can attempt to recover data that’s stored on bad sectors and clusters, but there’s a chance the data is lost forever. Writer Bio

What Are Bad Sectors   Bad Clusters  - 13