Hard disk drive platter

A hard disk drive platter or hard disk is the circular magnetic disk on which digital data is stored in a hard disk drive. The rigid nature of the platters is what gives them their name. Hard drives typically have several platters which are mounted on the same spindle. A platter can store information on both sides, typically requiring two recording heads per platter, one per surface. Platters for hard drives are some of the smoothest surfaces currently manufactured. Platters are manufactured, polished, and burnished in Cleanrooms, often 100 times cleaner than a hospital operating room, to ensure no contamination. This allows heads to fly at extremely low distances at a few nanometres enabling higher density than in the past.