Terabyte Explained

A terabyte (derived from the prefix tera- and commonly abbreviated TB) is a measurement term for data storage capacity. The value of a terabyte is based upon a decimal radix (base 10) and 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 x 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 without 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 and current usage, a terabyte (TB) contains 1,000,000,000,000 bytes = 1000⁴ or 10¹² bytes.
• According to traditional and binary arithmetic, a terabyte contained 1,099,511,627,776 bytes = 1024⁴ or 2⁴⁰ bytes. Ambiguity can be avoided by use of the standardized term for this quantity, the tebibyte.

The capacities of computer storage devices are traditionally advertised using their SI standard values.

Terabytes in use

• DreamHost offers its hosting customers 5 terabytes of monthly data transfer.^[1]
• Wal-Mart's data warehouse in Bentonville, Arkansas contains 500 terabytes of data as of 2004.^[2]However, this is expected, as of the first quarter of January 2008, to have reached somewhere in the region of 9 PB. Note the presence of Moore's Law.
• Second Life's total storage was estimated to consume 100 terabytes of server capacity in December 2007. The amount of data is rapidly growing.
• The U.S. Library of Congress Web Capture team has claimed that "as of May 2007, the Library has collected more than 70 terabytes of data"^[3]
• Ancestry.com claims approximately 600 terabytes of genealogical data with the inclusion of US Census data from 1790 to 1930.^[4]
• CASTOR at CERN has 10,000 TB of physics data.^[5]

• As of 2008, the largest 3.5 inch hard drive in the world, the Colossal Storage Corporation Atomic Holographic Drive, holds 100 terabytes of data using patented "3D Volume Holographic Optical Storage Nanotechnology". ^[6]

• YouTube.com offices hold over 6 terabytes full of user-submitted videos.

See also

• tebibyte
• terabit
• gigabyte
• petabyte
• binary prefix
• orders of magnitude (data)
• Terabyte is also the name of a fictional colonial termite that has become highly specialized in the documentary film The Future is Wild

Notes and References

1. http://www.dreamhost.com/hosting.html
2. Web site: At Wal-Mart, World's Largest Retail Data Warehouse Gets Even Larger. 2004-10-13.
3. Web site: About Web Capture. How large is the Library’s archive?. 2007-05-26.
4. Web site: Ancestry.com Adds U.S. Census Records. 2006-06-22.
5. Web site: Castor @ Cern website]. 2007.
6. Web site: Breakthrough Nanotechnology Will Bring 100 Terabyte 3.5-inch Digital Data Storage Disks.