Defragmenting your Hard Disk to improve performance
Hard Disk Drives explained
The Hard Disk is the primary means of storage for your computer with many useful properties, including:
- Extremely fast access compared to other forms of storage.
- Large capacity (typically a 20GB Hard Disk can hold the same amount of information as almost 14,000 floppy disks or over 30 CDs).
- Resilient - as long as the Hard Disk does not develop a fault your information is safe.
In addition, a Hard Disk is what is known as 'direct access' storage. This means that information can be directly retrieved from, or written to, any location on the disk (this is in contrast to media such as tape, where all data has to be read from the tape in a sequence until the required information is found).
A Hard Disk consists of various circular disks of magnetic material. Each of these disks has a 'read/write head' which is a device used to read or write data onto the surface of the disk.
By rotating the disks, and moving the read/write heads in and out, it is possible to access any location (and hence any information stored) on the Hard Disk.
A Hard Disk is made up of thousands of physical areas known as sectors. Each sector can contain an equal amount of information or data.
Files and Sectors
A single file will typically occupy many sectors. Ideally all the sectors that a file occupies will be adjoining as in the following diagram.
However, remembering that a Hard Disk is a direct access device it is possible that this is not the case. When files are saved to the Hard Disk, they will be broken up to fit the available free sectors. This is especially true after many files have been deleted, new files created or existing files edited ( all program files and temporary files created by Windows are also stored on the Hard Disk).
This results in a sector map that looks more like the following diagram.
The process of retrieving information from the Hard Disk consists of the computer rotating the disk to the required location and moving the read/write head in or out to locate specific sector(s). So, the more fragmented a file is, the more mechanical operations the Hard Disk must perform to retrieve it - this ultimately means that the process of reading and writing files to and from the Hard Disk gets slower, until eventually it has a negative and noticeable impact on the performance of the computer.
To resolve this problem and reverse the effects of fragmentation, Windows has a utility to defragment files and return the Hard Disk to a more organised state.
TopUsing Disk Defragmenter
To run the Disk Defragmenter utility click Start, All Programs, Accessories and System Tools to display the sub-menu that contains the Disk Defragmenter utility.
When you run the tool you will see a window similar to the following picture:
At the top, the Hard Disks installed in your computer are listed.
To find out whether you need to defragment a drive, first select it in the top part of the window (if you only have one drive it will probably be selected by default) - then click Analyze.
Analyses will take a minute or two, when it is complete you will be shown a message telling you whether the disk needs to be defragmented:
If you need to defragment the drive, close the message and click Defragment - this will reorganize the files. You will be able to watch the progress of the defragmentation in the 'Estimated disk usage after defragmentation' part of the window.
Be warned, depending on the size of your Hard Disk and the amount of data on it, this process could take a long time (mine takes 2-3 hours!)
Even if you are told that the disk does not need to be defragmented, if it has been a few months since the last time you did so it is worth running a defragmentation anyway.
I would advise against using the computer while it is performing a defragmentation of the Hard Disk.
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