Data access time is an important performance measure for any mass data storage system. It is the time between a data request received by the data storage system and the last bit of requested data sent to the host. For a magnetic hard disk drive, its data access time depends on how fast the actuator moves from tracks to tracks, the rotational speed of the platter, the size of the buffer for storing requests and data, and the algorithm that schedules the data requests. To improve the data access time, designers need to consider these parameters and perform trade-offs. This paper considers this problem. We derive analytical relations that are useful for design trade-offs.