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The amount of stored information, whether personal, business or government based, is growing at a prodigious rate. A little over six years ago the volume of worldwide information was calculated to be in the region of 50 terabytes or 50,000 gigabytes. Impressive as that figure might appear, it is dwarfed by the current estimate of three exabyte – an exabyte consists of a billion gigabytes. What this rapid rate of increase means is that every human being on Earth is churning out more than 333MB of data each on a yearly basis. This data-increasing surge brings with it the problem of deciding on an appropriate storage solution.

I can remember when flopping disks, with a capacity of 180KB, were the accepted standard. These 5.25 inch disks were soon replaced by a stream of floppy disks with increased storage capacity. Next on the scene was the CD-ROM with the ability to hold more than 500MB of data. As we all know, it wasn’t long before this amount of storage was considered inadequate for many tasks and DVD (Digital Versatile Disk) entered the picture. However this latest entry into the storage marketplace brought with it a certain amount of confusion with different formats competing for the purse strings of users.

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Currently there are six different DVD formats available. These are DVD-R, DVD-RW, DVD+R, DVD+RW, DVD-RAM and the recently introduced DVD+R DL (Double Layer). Each format has had some success although no clear winner has yet to emerge. Recent figures put the –R format slightly in the lead over +R with sales of blanks disks in 2004 at 611 million against 580 million respectively but the lead is expected to change by 2006 with –R reaching 1.54 billion and +R totally 1.8 billion.

This situation could be complicated by the arrival of three new formats that are waiting in the wings. However whatever the confusion, it will not slow down, and maybe increase, the sale of DVD drives. Sales of these drives currently stand at just under 48 million with some estimates having this total rise to 135 million drives by 2008.

Depending upon the chosen media and type of drive, various capacity sizes and transfer speeds will be available. For example, most of the available DVD formats will give you 4.7GB of storage (a double sided rewritable DVD-RAM disk allows 9.4GB of storage). DVD+R DL is capable of holding 8.5GB of data which will enable four hours of DVD-quality or 16 hours of VHS-quality video to be stored. Transfer rate speed is indicated by the “x” factor. Each “x” represents a speed of 1.38MB which means that 16x relates to a speed of 22MB a second. Currently the top speed for DVD+R DL is 2.4x or a transfer rate of 3.3MB a second.

Both DVD-R and DVD+R formats are write-only media and are best suited to storing large amounts of data, such as films or music, in one go. While Pioneer leads the support for DVD-R, DVD+R format has the support of companies such as Sony, Philips, Yamaha, Ricoh and Hewlett Packard. The DVD-RW and DVD+RW formats add the capability of being re-usable.

DVD-RAM, unlike the other formats, was designed for data processing applications. The media is divided into sectors in a similar way to a conventional hard disk. This format, championed by Toshiba, Hitachi and Panasonic, provides fast access to individual files and allows for data to be erased.

The new kid on the block, DVD+R DL, uses two thin embedded organic dye films that are used for data storage. A spacer layer sits between the two dye films. A focused laser modifies the physical and chemical structure of each layer so that areas have different optical properties to those of their surroundings so causing a variation in reflectivity. This provides a read-out signal that translates to the appropriate data.

In the future we can look forward to DVD-R DL offering similar functionality as DVD+R DL. Blu-ray format uses a laser diode emitting light with a wavelength of 405 nanometers (1 nanometer = 0.000001mm) and increases storage capacity up to 27GB. HD DVD uses the same laser-light wavelength as Blu-ray and is designed to offer 15 to 18GB on a single-sided DVD using MPEG-4 format.

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