Anatomy of a Hard Disk Drive

Inside the HDA

We removed the hard drive cover to show you how it looks like inside. Do not do this with you hard drive or you will damage it. If you are curious, open only defective hard drives (our hard drive was defective).

Figure 7: Main parts inside a hard drive.

The connector you see in Figure 7 is the opposite side of the connector in Figure 6.

The hard drive can have several discs. The one on our picture had three discs. There is one read/write read for each side of the disc – which is also called platter. The heads are stuck together in an arm. So, all the heads move together.

Figure 8: Several discs inside a hard drive.

A motor (actually the correct term is “actuator”) called voice coil moves the arm. It is called “voice coil” because it uses the same idea behind loudspeakers: a coil inside a magnetic field provided by a magnet. Depending on the current direction on the coil the arm moves to one side or to the other side. And depending on the intensity of the current, the actuator will move more or less. We removed the top “cover” (actually the top magnet) from voice coil and you can see it disassembled in Figure 9.

Figure 9: Voice coil actuator.

We removed the arm from the hard drive. You can see it in Figure 10. While we were removing it, we broke one of the heads (ops!). So, it should have six heads there but you will only see five (sorry, chief!)

Figure 10: Hard drive heads.