Inside: Platters and Heads
In order to increase the amount of information the drive can store, most hard disks have multiple platters. This drive has three platters and six read/write heads:
The mechanism that moves the arms on a hard disk has to be incredibly fast and precise. It can be constructed using a high-speed linear motor.
Many drives use a "voice coil" approach -- the same technique used to move the cone of a speaker on your stereo is used to move the arm.