Storage

Magnetic Discs



Magnetic storage refers to the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using one or more read/write heads. Magnetic storage media, primarily hard disks, are widely used to store computer data as well as audio and video signals. In the field of computing, the term magnetic storage is preferred and in the field of audio and video production, the term magnetic recording is more commonly used. The distinction is less technical and more a matter of preference.
The advantages of using magnetic storage are high storage capacity, reliable and give direct access to data. Hard discs also give us less time to access data because the access of data is very fast.











Optical Devices












Optical storage is a term refers to the storage of data on an optically readable medium. Data is recorded by making marks in a pattern that can be read back with the aid of light. A common modern technique used by computers involves a tiny beam of laser light precisely focused on a spinning disc. Optical storage differs from other data storage techniques that make use of other technologies such as magnetism or semiconductors. The term optical drive usually refers to a device in a computer that can read CD-ROMs or other optical discs.
The advantages are that CD-ROM's hold large quantities of data (650 MB) and they are relatively tough as long as the surface does not get too scratched. It is much faster to access than a floppy but it is currently slower than a hard disc.










Flash Memory
















Flash memory is non-volatile computer memory that can be electrically erased and reprogrammed. It is a technology that is primarily used in memory cards and USB flash drives for general storage and transfer of data between computers and other digital products. It is a specific type of EEPROM (Electrically Erasable Programmable Read-Only Memory) that is erased and programmed in large blocks; in early flash the entire chip had to be erased at once.

The advantages are that flash memory is non-volatile, which means that no power is needed to maintain the information stored in the chip. In addition, flash memory offers fast read access times (although not as fast as volatile DRAM memory used for main memory in PCs) and better kinetic shock resistance than hard disks. These characteristics explain the popularity of flash memory in portable devices. Another feature of flash memory is that when packaged in a "memory card," it is enormously durable, being able to withstand intense pressure, extremes of temperature, and even immersion in water.




Magneto-Optical Disc












A magneto-optical drive is a kind of optical disc drive capable of writing and rewriting data upon a magneto-optical disc. Both 130 mm and 90 mm form factors exist. The technology was introduced at the end of the 1980s. Although optical, they appear as hard disk drives to the operating system and do not require a special file system (they can be formatted as FAT, HPFS, NTFS, etc.).
The disc consists of a ferromagnetic material sealed beneath a plastic coating. There is never any physical contact during reading or recording. During reading, a laser projects a beam on the disk and according to the magnetic state of the surface, the reflected light varies due to the Magneto-optic Kerr effect. During recording, the laser power is increased so it can heat the material up to the Curie point in a single spot. This allows an electromagnet positioned on the opposite side of the disc to change the local magnetic polarization, and the polarization is retained when temperature drops.
The advantages of this storage are data authenticity and integrity, long-term data retention, high capacity and scalability and rapid information access.