However, optical storage has proven to be much slower and far less dense than magnetic storage and is much more adaptable to removable-media designs.
As such, optical storage is more often used for backup or archival storage purposes and as a mechanism by which programs or data can be loaded onto magnetic drives.
The encoding material sits atop a thicker substrate (usually polycarbonate) which makes up the bulk of the disc and forms a dust defocusing layer.
The encoding pattern follows a continuous, spiral path covering the entire disc surface and extending from the innermost track to the outermost track.
Unlike the 3½-inch floppy disk, most optical discs do not have an integrated protective casing and are therefore susceptible to data transfer problems due to scratches, fingerprints, and other environmental problems.
The instructions below can be used for both internal and external CD, DVD or Blu-Ray drives but some of the fundamentals might be a little different.Although most magnetic disk storage is fully read and write capable many times over, many optical storage media are either read-only or write-once.Note the convention in which we refer to magnetic as .The data is stored on the disc with a laser or stamping machine, and can be accessed when the data path is illuminated with a laser diode in an optical disc drive which spins the disc at speeds of about 200 to 4,000 RPM or more, depending on the drive type, disc format, and the distance of the read head from the center of the disc (inner tracks are read at a higher disc speed).Most optical discs exhibit a characteristic iridescence as a result of the diffraction grating formed by its grooves.