A head seek is a measure of performance relating to a rotating hard drive. The head seek time is the amount of time it takes for the head on the actuator arm of a disk drive to find the appropriate track on the disk on which to write or load information.
Once the hard disk receives a command to load or store data, an actuator arm attached to the hard disk guides the head of the arm to the appropriate track to find the correct sector. The head of the actuator arm will then either store data or read data from that sector, depending on the command. Current rotating hard disk drives have an average head seek time of approximately nine milliseconds. However, the very first hard disk drive had an average seek time of six hundred milliseconds in the late 1950's.