by Eric Brooks

Created on: May 05, 2009

It is often easy to forget that computers are composed of physical components and that there are actual, physical processes occurring beneath the hood of your system every time you perform a function. As with any other physical process, these moving parts require an amount of time to spin, read, move, or otherwise do whatever it is that they are doing. Defragmentation seeks to reduce this amount of time by lowering the amount of time it takes to find information on your hard disk drive. However, before delving into the mysteries of defragmenting, it is first necessary to explore how hard drives are actually put together.

HARD DISK DRIVE (HDD)

The hard drive in your computer is a physical component attached to the main motherboard with some type of cabling and also wired into your power supply where it obtains the electricity necessary to function. Regardless of whether you have a desktop or notebook computer, the composition of the hard drive is essentially the same. The drive contains one or more platters that can be compared to old vinyl records. These platters are broken up into a number of circular tracks that span the circumference of the disk, just like the grooves in a record. Each track is then divided into clusters, each of which is 4 kilobytes (KB.)

Unlike a CD or DVD, computer hard disks store information magnetically rather than optically. In every hard drive there is a read/write head at the end of an actuator. Continuing the vinyl record analogy, the read/write head is similar to the needle on a record player and the actuator is represented by the arm holding the needle above the record. However, unlike a vinyl record player, the read/write head on a hard disk drive does not actually touch the platters storing your information. Instead it hovers a short distance above the platter and alters the magnetic field of the information you are recalling or manipulating. In fact, if the head does touch the platter it can damage the disk drive during what is called a head crash.

Now that we have explored how hard disk drives are physically constructed, it is possible to discuss how information is stored onto them.

STORAGE

When a file is created, a software program installed, or something is downloaded to your computer, the information pertaining to that item is written magnetically onto your hard drive. As stated earlier, the smallest unit of measurement on a disk is the cluster which typically is capable of containing 4 KB of information. This means that all

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