Blu-ray Disc Technology
Blu-ray Disc Technology for Archival Storage
As storage media continued to develop and new formats evolved, improved technology and efficiency provided the possibility to store very large amounts of data, regardless of the type of requirements involved. The transfer rate and capacity of hard disk and tape-based technology, for instance, developed at a dramatic pace.
However, the biggest step forward in the flexible and standardized long-term storage of large amounts of data did not occur until the invention of the optical disc (CD - Compact Disc). The magic word associated with the optical disc is WORM (Write Once Read Many), or more precisely “True WORM”. With this development, the ideal means was available to store documents over a long period of time in a cost-effective manner, permanently, securely and immutably (audit-compliance).
The development of the third generation of optical media and drives, originally based on the CD and then on the DVD, is a particularly important milestone in increasing both capacity and read/write speeds. This technological leap forward also demonstrates that optical media continues to have a great deal of potential in terms of being able to increase their capacity. This breakthrough was achieved by using laser light of an even shorter wavelength. In contrast to the CD with 780nm or the DVD with 650 nm, the wavelength for the new BD medium is a mere 405 nm. This allows for very high recording densities on the discs coupled with a considerable reduction in access times.
The new technology is know by the abbreviation “Blu-ray®” and was supported by a consortium encompassing over 100 companies, including the founders Sony and Matsushita. The Blu-ray Disc (BD) has a recording density that is 6-7 times higher than that of the DVD. As a single layer format it offers 25 GB of storage capacity, as dual layer 50 GB. The maximum data rate of a first-generation BD is 9 MB/s at single reading rate. Drives with four-times (4x) reading rate are now available on the market, as are the corresponding media, and the upwards trend is set to continue.
Several Blu-ray DISC formats are available on the market: BD-ROM as a distribution medium, BD-RE for HD-TV recording in the film and television industry, and BD-R as a once-only recordable storage medium. The format often referred to as BD-RW, a re-writable PC storage medium, is actually the BD-RE format.