What is a Media Defect Table?

Older drives, like the Micropolis 1325, have a table sheet printed on one side of the enclosure. It says "Media Defect Table" and lists various numbers, cylinders, etc. This table denotes areas on the physical magnetizable surface of the drive's internal platters that an automated test had earlier discovered as faulty after production at factory. The drive will not be able to store data in these areas. Thus, the end user is required to manually enter the areas listed in this defect table into their storage driver, so the system using the drive will not try to store data at these locations.