Hard Disk Drives
How does a hard disk drive (HDD) work? A very basic explanation is that a recording head applies a magnetic field to a disk changing the bits of information on the disk as it rotates. The head can then read the information as it “flies” over these bits. Some of the components of a HDD are labeled below.
The spindle motor typically rotates the disk at 7200 RPM, and the suspension move across the disk to write on or read certain areas of the disk. The animation below shows how the suspension moves.
Click on the image to see animation.
Tribology comes into play as a result of the interaction between the recording head and the disk. In order for HDD capacity to keep increasing, the distance between the head and disk (flying height) needs to be lower than 5 nm. At this distance adhesion plays a large role, and the head has a greater chance of contacting the disk, a very undesirable but inevitable occurrence in the presence of shock loading. In order for the head to maintain a certain distance above the disk, it is shaped in such a way that there is a pressure build beneath it, much like an airplane wing. Shown below is an illustration of a head-disk interface (HDI) and animation of the head response to roughness