What primarily limits the speed of traditional HDDs?

The speed of traditional hard disk drives (HDDs) is primarily limited by mechanical arm movement. HDDs operate using a physical read/write head that moves across the spinning platters inside the drive. This mechanical movement takes time, and the speed at which the head can move to locate and read data significantly impacts the overall performance of the drive.

As the drive spins, the data is not immediately accessible; the read/write head must position itself accurately over the correct track on the disk. This process introduces latency, which means that even though the disks may spin at high RPMs (like 5400 or 7200 RPM), the time it takes for the arm to reach the desired location on the platter creates a bottleneck in data access speeds.

Other factors, such as the size of the drive, type of data connection, or type of power source, do not primarily dictate the speed in the same way. While these factors can influence performance, the mechanical nature of HDDs and the limitations of moving parts are the fundamental reasons why they cannot match the speeds of solid-state drives (SSDs), which utilize flash memory and have no moving components.