Computers are not just purely electrical devices.They also have moving components in them. These moving components take time to find themselves in the proper place to retrieve data. Some such components include DVD Drives, Hard Drives, CD drives,Floppy drives, and Zip Drives. There are varying cabling formats to each of these components including SCSI SATA IDE or a Floppy Ribbon some are even external like USB or IEEE but the point is that these devices require some time to retrieve data more so then say a USB flash drive or an SD micro Chip.
Each of these devices uses a magnetic head to create an imprint directly into some form of disc. The exception being DVD/CD ROMS. These actually use a laser to imprint tiny laser cuts upon a thin metal surface, but each of these devices reads that data in much the same way. By rotating the disc at a high rate of speed the device can scan the information contained on the disc like you would decrypt a Morris code message. Bits of information ones and zeros or long beeps and short beeps in varying patterns. Each of these devices has a “docked” position at which the head which reads data will remain until it’s needed, typically in the center of the disc.
When you delete an item from any of these this item does not really get deleted the device simply marks that area as unused despite the imprint still being there, further more the data is not moved around that imprint which is why deleted files can easily be retrieved with an undelete program.
Once these areas are marked as unwritten they will be written over first chance the drive has. So if you delete several mp3s that are 3 megs each. Then install a 20 meg program when the drive installs this program it will install from the center out and use every available area. This makes your program split into 4 sections. The program will fill the 3 separate 3 megs sections, then move on to fill the empty space at the end of the hard drive. As a result when you later try to retrieve this program, your hard drive will have to go all the way through the tracks to the outer most track before it can retrieve all of the data it needs.
Now that you have an idea of how these devices function. I’m sure you can see how you could potentially increase the speed of data retrieval?, that’s right defragmentation. The idea behind this method is that frequently used data such as boot sectors, and operating system components will be placed near the center of the disc where the heads dock when they aren’t being used. This way the head doesn’t have to move through as many tracks to reach its point of data collection for startup.
Another approach used by defragmenting programs is to take those imprints where data has been deleted, and fill them with the surrounding data. Thus an extra effect of doing this is that you will no longer be able to retrieve that deleted data. The Data has been literally written over. By transferring the existing data around these empty imprints the defragment program can place programs, and picture data back into one place. That way they all remain in a line. This is also important for DVD/CD based software, and music the first tracks go in the center. Then it works it’s way out keeping all the data in a nice single file line. By doing this the read heads don’t have to move very far to retrieve data.
A poorly formatted DVD/CD may cause your drive to make a lot of noise this is due to how much the head is being required to move to read the next bit of data you may also notice this effect if you have finger prints, or scratches on your dvd drive. The laser reads the imprints in the film through a plastic protective layer. If this protective layer has been breached the laser tends to be reflected away from the data it needs. This will cause the head to continue to move around attempting to focus much like you would have to attempt to focus with finger prints upon your glasses, or slime in your eye.
Fortunately hard drives aren’t susceptible to this method of corruption, and corrosion is unlikely. The discs inside a hard drive are coated with Platinum which does not tarnish, or corrode. however this fragmentation which occurs, due to the placement of new data and deletion of old data. Makes empty spaces in between and can create the same effect as a scratched CD. A badly fragmented hard drive may be heard from time to time making groaning noises.
By regularly defragmenting your hard drive you can avoid this. Temporary files are always being added and deleted as you browse the Internet this can cause fragmentation so it’s important to defragment regularly.