Blu-ray Disc
 

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Blu-ray Disc (also known as Blu-ray or BD) is an optical disc storage medium. Its main uses are high-definition video and data storage. The disc has the same physical dimensions as standard DVDs and CDs.
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The name Blu-ray Disc is derived from the blue laser (violet-colored) used to read and write this type of disc. Because of the beam's shorter wavelength (405 nanometres), substantially more data can be stored on a Blu-ray Disc than on the DVD format, which uses a red (650 nm) laser. A two-layer Blu-ray Disc can store 50 gigabytes, almost six times the capacity of a two-layer DVD, or ten times that of a single-layer DVD.

During the format war over high-definition optical discs, Blu-ray Disc competed with the HD DVD format. On February 19, 2008, Toshiba—the main company supporting HD DVD—announced that it would no longer develop, manufacture, and market HD DVD players and recorders,[2] leading almost all other HD DVD companies to follow suit, effectively ending the format war.
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Blu-ray Disc was developed by the Blu-ray Disc Association, a group representing makers of consumer electronics, computer hardware, and motion pictures. As of November 6, 2008, more than 1030 Blu-ray Disc titles have been released in the United States and more than 570 Blu-ray Disc titles have been released in Japan.[3][4][5] There are expected to be over 1300 Blu-ray Disc titles released in the United States by the end of 2008.[6]

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Type	Physical size	Single layer capacity	Dual layer capacity
Standard disc size	12 cm, single sided	25 GB (23.28 GiB)	50 GB (46.56 GiB)
Mini disc size	8 cm, single sided	7.8 GB (7.26 GiB)	15.6 GB (14.53 GiB)

Recording speed

Drive speed	Data rate		Write time for Blu-ray Disc (minutes)
	Mbit/s	MB/s	Single Layer	Dual Layer
1×	36	4.5	90	180
2×	72	9	45	90
4×	144	18	23	45
6×	216	27	15	30
8×*	288	36	12	23
12×**	432	54	8	15

* On August 8, 2008, Japanese electronics company Buffalo announced that it will ship the first 8x Blu-ray burners in Japan starting from September 2008. On September 22, 2008, Buffalo announced one internal and one external 8x Blu-ray burners for the United States, to be released the same month.The following day Sony announced the BWU-300S, an internal 8x Blu-ray burner for the United States.

** Theoretical