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Wednesday, February 10, 2010

Tertiary Storage Devices - Removable Disks

Tertiary storage or tertiary memory, provides a third level of storage. Typically it involves a robotic mechanism which will mount (insert) and dismount removable mass storage media into a storage device according to the system's demands; this data is often copied to secondary storage before use. It is primarily used for archival of rarely accessed information since it is much slower than secondary storage (e.g. 5–60 seconds vs. 1-10 milliseconds). This is primarily useful for extraordinarily large data stores, accessed without human operators.
Examples : Removable disks, magnetic tapes, CD-ROMs etc.

Removable Disks : A removable disk is a type of media that enables a user to easily move data between computers without having to open their computer. Examples :

* Floppy diskettes : A Floppy Disk Drive, or FDD for short, is a computer disk drive that enables a user to easily save data to removable diskettes. They are made from a thin flexible disk coated with magnetic material, enclosed in a protective plastic case/
* CD disc/DVD disc/Blu-ray disc : A compact disc is a flat round storage medium that is read by a laser in a CD-ROM drive. The standard CD is capable of holding 72 minutes of music or 650 MB of data. 80 minute CDs are also commonly used to store data and are capable of containing 700 MB of data.
Digital Versatile Disc or Digital Video Disc, DVD or DVD-ROM is a type of disc drive that allows for large amounts of data on one disc the size of a standard Compact Disc.
Blu-ray Disc, BD or BD-ROM is an optical disc that is capable of storing up to 25 GB on a single layer disc and 50 GB on a dual layer disc.
* Tape drive cartridges : A magnetically thin coated piece plastic wrapped around wheels that is capable of storing data. Tape is much less expensive than other storage mediums but commonly a much slower solution that is commonly used for backup.
* Thumb drives : It is a portable drive that is often the size of your thumb that connects to the computer USB port. Today flash drives are available in various sizes including but not limited to 256MB, 512MB, 1GB, 5GB, 16GB, and beyond and are widely used as an easy and small way to transfer AND store information from their computer.

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