15. Optical storage, forms of optical storage. Magneto-optical disc storage. Online data storage.

Optical storage, the typical optical disc, stores information in deformities on the surface of a

circular disc and reads this information by illuminating the surface with a laser diode and observing

the reflection. The deformities may be permanent (read only media ), formed once (write once media) or reversible (recordable or read/write media). Optical disc storage is non-volatile. Optical disks can store information at much higher densities than magnetic disks. Thus, they are ideal for multimedia applications where images, animation and sound occupy a lot of disk space.

The following forms of optical storage are currently in common use:

 CD, CD-ROM, DVD, BD-ROM (read only memory): Read only storage, used for mass distribution of digital information (music, video, computer programs), you cannot change data stored on them.

 CD-R, DVD-R, DVD+R BD-R (recordable): Write once storage, used for tertiary and off-line storage; write-once devices which let you duplicate CDs.

 CD-RW, DVD-RW, DVD+RW, DVD-RAM, BD-RE (Blue Ray) (rewritable): Slow write, fast read storage, used for tertiary and off-line storage, the disks enable you to write onto them in multiple sessions, like a hard disk and can be erased and reused many times.

 DVDs (digital versatile discs) are similar in size to CDs (both are 1.2 mm thick), but they differ in structure and capacity. DVDs have more tracks and more pits (tiny holes) per track, and can store from 4.7 GB to 17 GB of data, movies, high-definition sound, etc.,; so they will probably replace CDs.

 Ultra Density Optical or UDO is similar in capacity to BD-R or BD-RE and is slow write, fast read storage used for tertiary and off-line storage.

Online data storage

Recent developments have enabled users to store their data on the internet. This is precisely what online data storage is all about. The rapid technological advancements taking place have brought the price of broadband internet down. This has been coupled with better service and better speed which has driven many people to purchase online data storage.

Online data storage benefits the user in more than one way.

 Primarily, it is an additional and flexible source for storing data.

 Secondly, it also serves as a backup mechanism.

 Thirdly, it serves as an effective method through which users can share their data with

others on the internet.

Another advantage is the opportunity to expand when you need to. Once you reach the maximum limit of storage you can expand your storage capacity by purchasing additional space. Online data storage allows the users to access their data from any location whatsoever.

Magneto-optical disc storage is optical disc storage where the magnetic state on a ferromagnetic surface stores information. The information is read optically and written by combining magnetic and optical methods. Magneto-optical disc storage is non-volatile, sequential access, slow write, fast read storage used for tertiary and off-line storage. Consequently, MO disks are rewritable, i.e. they can be written to, erased, and then written again.