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As anyone who has worked with a computer will know, a hard drive is one of the most important parts of your computer. Although it is a complex piece of hardware and installing one can sometimes be a chore, a little knowledge and practice can make it very easy. The process of replacing or installing hard drives can make you very nervous, but it doesn't have to.

This section of the site is written to help you decide on various types, learn how they work, and explain how to install a drive and conveniently prepare it for use.

All hard drives share the same basic structure, varying only in how each part is used and the quality of the parts themselves. The platters, spindle motor, heads, and head actuator are inside the drive, sealed from the outside. This chamber is often called the head disk assembly (HDA). The HDA is rarely opened, except by professionals. On the outside are the logic board, bezel, and mounting equipment. Below, I will describe each of these components.



The platters are the disks inside the drive. Platters can vary in size. Often the size of the drive, 5.25" or 3.5", is based on the physical size of the platters. Most drives have two or more platters. The larger capacity drives have more platters. They are usually made of an aluminum alloy so that they are light. The newest and largest drives make use of a new technology of glass/ceramic platters. Basically, this is glass with enough ceramic within to resist cracking. This glass technology is taking over aluminum in the hard drive industry. Many popular manufacturers already use it, including Maxtor, Toshiba, and SeaGate. Glass platters can be made much thinner than aluminum ones, and they can better resist the heat produced in operation.

Alone, platters are not capable of recording data. Each one is coated with a film of some magnetically sensitive substance. The oxide media is one of the ways of doing this. A mixture of compound syrup is poured on the platter, then spun to evenly distribute the film over the entire platter. This substance has iron oxide as a main ingredient, explaining why many platters you may see will be brownish-orange. The other main media consists of a thin film of a cobalt alloy which is placed on the platter through electroplating, much like chrome.

The read/write heads do just that, they read and write to the platters. There is usually one head per platter side, and each head is attached to a single actuator shaft so that all the heads move in unison. Each head is spring loaded to force it into the platter it reads. When off, each head rests on the platter surface. When the drive is running, the spinning of the platters causes air pressure that lifts the heads ever-so-slightly off the platter surface. The distance between the head and platter is very small...so small that the HDA must be assembled in a clean room because one dust particle can throw the whole thing off. This sensitivity and accuracy is what causes only bigger companies to be able to repair hard drives simply because of the expense of a clean room. A slider is attached to each head. This mechanism actually glides over the platter and holds the head at the correct distance to do its job.