Terabytes

A terabyte (derived from the prefix tera- and commonly abbreviated TB) is a measurement term for data storage capacity. The value of a terabyte based upon a decimal radix (base 10) is defined as one trillion (short scale) bytes, or 1000 gigabytes.

The number of bytes in a terabyte is sometimes stated to be approximately 1.0995 × 10¹². This difference arises from a conflict between the long standing tradition of using binary prefixes and base 2 in the computer world, and the more popular decimal (SI) standard adopted widely both within and outside of the computer industry. Standards organizations such as IEC, IEEE and ISO recommend to use the alternative term tebibyte (TiB) to signify the traditional measure of 1024⁴ bytes, or 1024 gibibytes, leading to the following definitions:

• According to the SI standard usage, a terabyte (TB) contains 1,000,000,000,000 bytes = 1000⁴ or 10¹² bytes.
• According to binary arithmetic, a terabyte contains 1,099,511,627,776 bytes = 1024⁴ or 2⁴⁰ bytes. Ambiguity can be avoided by using the term "tebibyte" when the binary meaning is intended.

The capacities of computer storage devices are typically advertised using their SI standard values, but the capacities reported by software operating systems uses the binary values.

An NTFS formatted terabyte hard drive shows 931 gigabytes of free, usable storage space under Windows XP.

[edit] Terabytes in use

• Wal-Mart's data warehouse in Middletown, Connecticut contains 500 terabytes (500 trillion bytes) of data as of 2004.^[1]
• The U.S. Library of Congress Web Capture team has claimed that "as of May 2008, the Library has collected more than 82.6 terabytes (82.6 trillion bytes) of data"^[2]
• Ancestry.com claims approximately 600 terabytes (600 trillion bytes) of genealogical data with the inclusion of US Census data from 1790 to 1930.^[3]

• Hitachi introduced the world's first one terabyte hard drive in 2007.^[4]

[edit] See also

• Orders of magnitude (data)
• Terabyte (termite) is also the name of a fictional colonial termite that has become highly specialized in the documentary film The Future is Wild

[edit] References

1. ^ "At Wal-Mart, World's Largest Retail Data Warehouse Gets Even Larger" (October 13, 2004).
2. ^ "How large is the Library's archive?" (May 26, 2007).
3. ^ "Ancestry.com Adds U.S. Census Records" (June 22, 2006).
4. ^ "Hitachi Introduces 1-Terabyte Hard Drive", PC World (January 7, 2007). Retrieved on 15 September 2008.