Storage Media	Hard Disks	DVD Disc
Optical Discs	Tape Media	Flash Drive
Zip Catridges	RAID	Removable Media
(U)niversal (B)us (S)erial

What is DVD?

Introduced to the market in year 1997, DVD (also known as Digital Versatile Disc or Digital Video Disc) has become the latest generation of optical disc storage technology. Even though it's physical dimension is the same with compact discs (i.e. 8cm or 12cm in diameter), DVD takes its advantages of having much higher density with a single data format. Minimum DVD storage of data is 4.7GB; however its maximum storage capability can be up to 26 times as much as a standard CD-R. Compared with CD technology, DVD allows for better quality of graphics, resolution and surrounded sound. Nowadays, DVD's widespread has gain support from major numbers of electronic companies, computer hardware companies, and also music and audio studios all over the world.

DVD ARCHITECTURE

DVD is a 0.6mm thick disc made of poly-carbonate plastic and has a very much thinner reflective layer made of gold or aluminium. Two 0.6mm discs are joined together to form a 1.2mm thick DVD bonded-disc that allows data to be read from either one side (single-sided) or two sides (double-sided) by laser beam.

In DVD, lens with higher Numerical Aperture (i.e. NA) is achieved to refine the laser assembly; hence allow usage of lesser smaller pits and narrower tracks. Modulation scheme of 8 to 17 (EFM PLUS) is used to provide DVD more efficient backward compatibility.

Another special and outstanding feature adopted by DVD is the powerful technique of error correction to recover from even large scratches with nearly no loss of data. The RS-PC (Reed Solomon Product Code) is used in this technique which allows as 10 times more robust than which is currently used in CD system. Also, DVD is provided with several configurations of data reader ranging from 2D to 3D storage. Each configuration allows different additional storage capacity.

DIFFERENT FORMATS OF DVD

DVD-ROM

Provide high-capacity computer ROM storage. Data types stored range from multimedia, computer games, interactive systems to databases. DVD includes variety of recordable variations including DVD-R, DVD-RAM, DVD+RW and DVD-RW D-ROM

DVD-Audio

Provides far higher quality surround-sound music with increased playing time.

DVD-Video

Provides high-quality multi-lingual movies on one disk with random-access to episodes and surround-sound audio.