Optical Disks
by: jameswalsh
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They are thus of no help when you have to transport data from one device to another. That is why a range of portable data storage devices have been invented, such as floppy disks, portable hard disks, optical disks, USB drives and tape drives.
All of these are quite light and transportable. Out of these, optical disks today rule unchallenged in the market of portable and light data storage media. There is hardly any new computer or laptop which does not ship out with optical drives.
Optical Disk Technology
Optical disks are in the shape of small platters made of polycarbonate plastic that you can easily hold in your palm. They are quite thin but amazingly tough and require a lot of effort to snap into pieces. They hold data on only one side which is called the data recording surface. The other side is called the label side.
An optical disk records data as a single groove consisting of microscopic pits that starts around the hole in the centre of the disk and goes around again and again, moving its way toward the edges. This grove is so thin and tightly packed that if stretched straight in a single line, it would be 5-km long! Each pit on the groove represents one and its absence zero, thus making possible recording data in the digital format.
Optical disks are used in conjunction with optical drives. Once the disk is inserted in the drive, it begins to be spun very fast by a motor. Right above the disk is situated a read / write head that emits a laser and moves back and forth. The laser emitted by the head hits the disk surface and bounces back to the head where it gets read and interpreted by the operating system. In this way, data on the disk is passed on to the computer for processing.
Types of Optical Disks
Optical disks are of two types: compact disks (CDs) and digital video disks (DVDs). The former is the older version that has a capacity of about 700 MB. Later, as the technology matured, another version of optical disks, DVDs, was introduced. The latter has a whopping 4.6 GB capacity which is sufficient to hold a full-length Hollywood movie or hours of music.
Both CDs and DVDs come in two main versions: writable and rewritable. In the former, the blank data recording surface can be written over only once. These type of disks are ideal for uses such as recording songs and movies. Rewritable CDs and DVDs, as the name suggests, are for multiple use. They can be written over about a 1,000 times by erasing the previous data and over-writing it with new one. These disks are ideal for taking data backups or using them as mini hard drives.
Pros and Cons of Optical Disks
Optical disks offer many benefits to the user compared to other data-storage media. First of all, they are extremely cheap compared to tape drives or USB drives. They are very light and can easily be carried in your hand or pocket. A large number of CDs and DVDs can be stacked over one another in a small box without taking too much space on your table.
Optical disks are also very tough and very difficult to bend or break. In addition to these physical features is the phenomenal data-storage capacity. These disks offer an unbeatable combination of cost per MB of data stored. They do not have many disadvantages, except that, unlike USB drives, to use an optical disk you have to first invest in an optical drive.
How can Optical Disks Suffer Data Loss
For all their benefits, it is also a harsh fact that data does get lost from optical disks. This can happen due to many reasons related to both software and hardware. The most common cause of data loss is damage to the data-recording surface.
If you spill something on the disk or cause it to be scratched, this will smudge the pattern of pits etched on its surface. Consequently, the drive will not be able to read it and data loss will occur. Allowing the disk to lie in direct sunlight or next to a heat source will also result in damage to the data-recording surface.
Data can be lost due to software errors as well. The user may delete a file accidentally or even reformat a rewritable disk, thus wiping off all data. Virus attacks and software corruption also lead to files on the disk becoming inaccessible.
About the Author
James Walsh is a freelance writer and copy editor. If you are concerned about data loss and would like more information on Data Recovery see http://www.fields-data-recovery.co.uk
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