Storage Devices

Optical, Magnetic and Solid State

Optical Storage

Optical storage devices save data as patterns of dots that can be read using light. A laser beam is the usual light source.

The data on the storage medium is read by bouncing the laser beam off the surface of the medium. If the beam hits a dot it is reflected back differently to how it would be if there were no dot. This difference can be detected, so the data can be read.

Dots can be created using the laser beam (for media that is writable such as CD-Rs). The beam is used in a high-power mode to actually mark the surface of the medium, making a dot. This process is known as ‘burning’ data onto a disc.

Magnetic Storage

Magnetic storage is a storage medium commonly used for large volumes of data (e.g., video, image, or remote sensing data). Magnetic tape drives use magnetic tape to store the data. Large amounts of data are stored through tape drives because the capacity on the drives is huge - three billion (or three gigabits) of data per square inch can fit on a single magnetic disk.

Magnetic media is made up of a thin layer that can record a magnetic signal supported by a thicker film backing. The top coat consists of a magnetic pigment. The binder holds the magnetic particles together. The magnetic layer (top coat) records and stores the magnetic signals that are written to it. The backing film supports the magnetic top coat and reduces tape friction and distortion.

Solid State Storage

The term ‘solid-state’ essentially means ‘no moving parts’.

Solid-state storage devices are based on electronic circuits with no moving parts (no reels of tape, no spinning discs, no laser beams, etc.)

Solid-state storage devices store data using a special type of memory called flash memory.

Examples of these are:

Magnetic based drives, for example:-

Hard disk

Floppy Disk

Magnetic tape

Optical based drives, for example:-

CD drive (ROM and RW)

DVD drive (RPM and RW)

Flash or solid state chip based drives, for example:-

USB drive

SD cards.