A terabyte is a SI-multiple (see prefix tera) of the unit byte for digital information storage and is equal to 10¹² (1000000000000) bytes or 1000 gigabytes. The unit symbol for the terabyte is TB.

The designation terabyte is rarely used to refer to the tebibyte, its binary prefix analogue, because only recent (since 2007) disk drives have this capacity. Disk drive sizes are always designated in SI units by manufacturers. However, a possible confusion arises from this definition with the long-standing tradition in some fields of information technology and the computer industry of using binary prefix interpretations for memory sizes. Standards organizations such as International Electrotechnical Commission (IEC), Institute of Electrical and Electronics Engineers (IEEE) and International Organization for Standardization (ISO) recommend to use the alternative term tebibyte to signify the traditional measure of 1024⁴ bytes, or 1024 gibibytes, leading to the following definitions:

• In standard SI usage, 1 terabyte (TB) equals 1000000000000bytes = 1000⁴ or 10¹² bytes.
• Using the traditional binary interpretation, a terabyte is 1099511627776bytes = 1024⁴ = 2⁴⁰ bytes = 1 tebibyte (TiB).

The capacities of computer storage devices are typically specified using their the standard SI meaning of unit prefixes, but many operating systems and applications report in binary-based units. Mac OS X 10.6 (Snow Leopard) reports decimal units.

[edit] Examples of terabyte usage

Examples of the use of "terabyte" to describe data sizes in different fields are:

• Library data - The U.S. Library of Congress Web Capture team has claimed that "As of May 2009, the Library has collected almost 100 terabytes of data".^[1]
• Online data bases - Ancestry.com claims approximately 600 TB of genealogical data with the inclusion of US Census data from 1790 to 1930.^[2]
• Computer hardware - Hitachi introduced the world's first one terabyte hard disk drive in 2007.^[3]
• Internet traffic - In 1993, total Internet traffic amounted to approx. 100 TB for the year.^[4] As of June 2008^[update], Cisco Systems estimated Internet traffic at 160 TB/s (which assuming to be statistically constant comes to 5 zettabytes for the year).^[5]
• Social networks - As of May 2009, Yahoo! Groups had "40 terabytes of data to index" ^[6]
• Video - Released in 2009, the 3D animated film Monsters vs. Aliens used 100 TB of storage during development.^[7]
• Usenet messages - In October of 2000, the Deja News Usenet archive had stored over 500 million Usenet messages which used 1.5 TB of storage^[8]

[edit] See also

• Orders of magnitude (data)

[edit] References