What Is the Function of a Hard Disk's Actuator?

function-hard-disk-s-actuator Credit: Diane Macdonald/Stockbyte/Getty Images

A hard disk's actuator is the electronic device that moves the actuator arm across the hard disk's platter, and it works hand in hand with other components to locate, write, read or delete information. The actuator assembly operates similarly to how a record player plays a vinyl record.

The head actuator assembly of a hard disk is composed of the main actuator motor, coils, axles, sliders and two or three actuator arms that span the disk's magnetic platter. The read/write heads are positioned on the tips of actuator arms to locate data quickly.

CD, DVD and Blu-ray drives also use the same technology to read and write data. However instead of having a magnetic head to read and write data, optical drives have optical lenses that shoot laser to access and store data on discs. An actuator arm guides the optical lens equipped with a photodiode that detects reflected light across the surface of the disc to read and write data.

Older actuators are powered by stepping motors, which are prone to overheating that lead to corrupted data. A stepping motor needs to be parked first before it can read or write data. This design flaw often leads to miscalculated movement timings and mistakes in storing data.

Newer actuators use linear motors made up of magnetic coils, which greatly improve data integrity and the accuracy of actuator arm movements.