How to Protect Discs (CDs, DVDs) from Data Loss

By: Jamie Wallis
Do They Make Good Backup Media? Computers are digital machines, that is, they can only process information by converting them into a digital form. In their routine operations, computers generate a huge amount of digital data. This has to be stored somewhere for safety and easy access. The primary storage device in a computer is a hard disk. It is made up of many circular platters that have a magnetic coating on the surface. All data is stored on this surface as distinct patterns which are read by a read / write head. Hard disk is a non-removable storage media – it is screwed to the insides of a CPU and is connected to the motherboard. (This is why it is also referred to as Fixed Disc Drive or FDD for short.) This poses a problem. What if one has to carry some data with them to another location? To fulfil this need, a variety of portable (removable) digital storage devices have been invented. These use different ways to store data – as magnetic patterns, electric charge or an etched surface – and are quite small and can easily fit into a shirt pocket. Some examples include flash memory cards, USB drives, CDs, DVDs and floppies. Currently, the most popular removable data storage media in the world is the optical discs. These are of two types – compact discs (CDs) and Digital Versatile Discs (DVDs). Both of these are circular discs made of plastic. These can be further subdivided into two categories – those that can be written only once and others which can be written over again and again by deleting the previous data.

The CDs were introduced in the early 80s originally to store audio files for use with music equipment. Seeing their popularity and features, they were quickly adapted for use in computers too. A CD can typically store about 700 MB of data, which is a huge leap over earlier portable storage media like floppy disks that could only store data of about 1.44 MB size. Amazingly, a CD can store data worth 500 floppies! The introduction of CDs fulfilled a long-felt need for a portable storage media – light and small – that could carry a substantial amount of data easily. The DVDs are a further development of the CD technology. They are of the same size as the latter but hold about 4.7 GB of data. This means that a DVD can hold as much data as about 7 CDs. One key feature of DVDs is that some of them can store data on two layers on the same surface and increase the data capacity to a whopping 8.5 GB. All optical discs have a shiny surface on which is written data as a pattern of microscopic pits. This is read by a laser which bounces off from the surface back to the sensor (this is why CDs and DVDs are called optical discs). Each pit represents 1 and its absence represents 0, thus allowing data to be stored in a digital form. CDs and DVDs are very tough, made of durable plastic. They do not disintegrate and get bent or broken till a considerable force is applied. Data on them can safely be stored for a long time. These are ideal for home users and corporate executives because their capacities ensure that they can accommodate all the data files that are ordinary generated and saved by the users. Optical discs are quite portable and light and many of them can be carried around in a small box. The only consideration in maintaining CDs and DVDs is to ensure that their surface remains clean of all stains and blotches and it does not get scratched. Such surface corruption can damage the patterns of pits that are read by the laser. If this happens, the computer cannot comprehend what is written on the disc and data loss occurs. When not being used by the computer, the disc should always be kept enclosed in a plastic case to protect it from dust and scratches. It should also be periodically cleaned by a soft cloth to remove all smudges and surface contamination that may have crept in. Also, optical discs should not be left exposed to sunlight or kept near a heat source as that may damage the data or disfigure their shape. DVDs and CDs are one of the cheapest and most durable removable storage media available in the market. With a little care, they can safely store your data for a number of years.

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