How a Hard Drive Works
A Simple Guide to the
Inner Workings of a Hard Drive

One or more platters are mounted on a spindle inside the hard drive case. Both side of the platters are covered with a magnetic material. The spindle is mounted to a motor that spins the platters.

Mounted to the end of an arm are the heads. The arm moves back-and-forth across the platters to position the head, much like a record player.

The heads read and write the data to the platters by detecting or changing the characteristics of the magnetic material. Similar to a CD, the data is laid out in tracks (also called cylinders) on the platters.

To protect the magnetic material, the heads do not touch the platters when they are spinning. They “float” fractions of a millimeter above them on a cushion of air.