Offline Storage Devices

Offline Storage Devices

1. CD

   • CD players are neither mechanical nor magnetic but optical. They use flashing laser lights to record and read back information from the shiny metal discs. In a CD player, the only thing that touches the CD is a beam of light. Another advantage is that the CD player can move its laser quickly to any part of the disc, so you can instantly flip from track to track or from one part of a movie to another. The data is stored just like DVDs or Blu-Ray disks, on magnetic strips or tracks

2. DVD

   • DVDs are of the same diameter and thickness as CDs, and they are made using some of the same materials and manufacturing methods. Like a CD, the data on a DVD is in the form of small pits and bumps in the track of the disc. Each writable layer of a DVD has a spiral track of data. On single-layer DVDs, the track always circles from the inside of the disc to the outside.

3. DVD - RAM

   • The structure of a DVD-RAM is closely related to older hard disk and floppy disk technology, as it stores data in concentric tracks. DVD-RAM has numerous rectangles on the surface that define the boundaries of data sectors. This is how the data is stored.

4. Blu-Ray Disks

   • The name "Blu-ray Disk" is derived from the blue-violet laser used to read and write this type of disc. Because of its shorter wavelength (405 nm), more data can be stored on a Blu-ray Disc than on the DVD format, which uses a red, 650 nm laser. The main advantage when compared to tape is that the optical media is archival, lasting for over 50 years.

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