Terabyte

The terabyte is a multiple of the unit byte for digital information. The prefix tera means 10¹² in the International System of Units (SI), and therefore 1 terabyte is 1000000000000bytes, or 1 trillion (short scale) bytes, or 1000 gigabytes. 1 terabyte in binary prefixes is 0.9095 tebibytes, or 931.32 gibibytes. The unit symbol for the terabyte is TB or TByte, but not Tb (lower case b) which refers to terabit.

Usage

Disk drive sizes are always designated in SI units by manufacturers, which is clearly marked on the packaging. Still, confusion may arise 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, 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 High ISO IEEE number of the terabyte means it can be thought of a physical form of memory, of which the singular byte cannot be. The capacities of computer storage devices are typically specified using 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 SI units.

Illustrative usage examples

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 claims that "As of April 2011, the Library has collected about 235 terabytes of data" and that it adds about 5 terabytes per month.^[1]
• Online databases – 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]
• Historical Internet traffic – In 1993, total Internet traffic amounted to approximately 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] In other words, the amount of Internet used per second in 2008 exceeded all of the Internet used in 1993.
• 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 2000, the Deja News Usenet archive had stored over 500 million Usenet messages which used 1.5 TB of storage.^[8]
• Encyclopedia – Wikipedia's January 2010 raw data uses a 5.87 terabyte dump.^[9]
• Climate science – In 2010, Germany's Climate Research Centre (DKRZ) was generating 10,000 TB of data per year, from a supercomputer with a 20 TB memory and 7,000 TB disk space.^[10]
• Audio – One terabyte of audio recorded at CD quality will contain around 2,000 hours of audio. Additionally, one terabyte of compressed audio recorded at 128 kB/s will contain about 17,000 hours of audio.
• The first 20 years worth of observations by the Hubble Space Telescope has amassed more than 45 terabytes of data. ^[11]
• The IBM computer Watson, in which Jeopardy! contestants competed against in February 2011, has 16 terabytes of RAM.^[12]

See also

• Orders of magnitude (data)

References