DVD

With the same overall size as a standard 120mm diameter, 1.2mm thick CD, DVD discs provide up to 17GB of storage and come in four versions:

  • DVD-5 is a single-sided single-layered disc boosting capacity seven-fold to 4.7GB
  • DVD-9 is a single-sided double-layered disc offering 8.5GB
  • DVD-10 is a 9.4GB dual-sided single-layered disc
  • DVD-18 will increase capacity to a huge 17GB on a dual-sided dual-layered disc.

DVD layers

The tracks on a DVD are placed closer together, thereby allowing more tracks per disk. The DVD track pitch (the distance between each) is reduced to 0.74 micron, less than half of CD’s 1.6 micron. The pits, in which the data is stored, are also a lot smaller, thus allowing more pits per track. The minimum pit length of a single layer DVD is 0.4 micron as compared to 0.834 micron for a CD. With the number of pits having a direct bearing on capacity levels, DVD’s reduced track pitch and pit size alone give DVD-ROM discs four times the storage capacity of CDs.

DVD pitch

Read page 52 of the textbook “Exploring Computer Hardware”.