Petabyte - Definition and Overview

A petabyte is a unit of measurement in computers of one thousand million million (short-scale quadrillion) bytes. Its abbreviation is PB.

Because of irregularities in definition and usage of the kilobyte, the exact number in common practice could be either one of the following:

1. 1,000,000,000,000,000 bytes - or 10¹⁵.
2. 1,125,899,906,842,624 bytes - 1024⁵, or 2⁵⁰. This is 1024 times larger than a terabyte. This is the definition most often used in information storage.

An exabyte is 1000 times a petabyte using the first definition, or 1024 times a petabyte using the second definition. A petabyte is either 1000 terabytes or 1024 terabytes, depending on the usage.

Petabytes in use

The San Diego Supercomputer Center (SDSC) in the USA has a 1 petabyte hard disk store and a 6 petabyte robotic tape store, both attached to the National Science Foundation's TeraGrid network. (Source: Electronics Weekly, Dec 11, 2002)

The Internet Archive Wayback Machine contains approximately 1 petabyte of data and is currently growing at a rate of 20 terabytes per month. (Source: Internet Archive FAQ (http://www.archive.org/about/faqs.php#9))

NOB Cross Media Facilities (http://www.nob.nl/index.cfm?cfid=33000632&cftoken=2193809&ln=en#) in the Netherlands employs a 1.5 Petabyte storage network for the storage of all old and new public television and radio content in digital format. Within the next year, most Dutch public television content will be pulled directly out of this database during broadcast.

Distinction between 1000 and 1024 terabytes

To clarify the distinction between decimal and binary prefixes, the International Electrotechnical Commission (IEC), a standards body, in 1998 defined new prefixes by combining the International System of Units (SI) prefixes with the word "binary" (see Binary prefix). Thus meaning (2) is called by the IEC a pebibyte (Pib), and meaning (1) is called by the IEC a petabyte. This naming convention has not, as of 2004, been widely adopted.

Origin of prefix

The prefix peta- is an alteration of the Greek prefix penta-, from the word pente, meaning 5.

See also

• exabyte
• terabyte
• Binary prefix
• integral data type.

External links

• http://www.quinion.com/words/turnsofphrase/tp-kib1.htm
• http://www.nist.gov/public_affairs/techbeat/tb9903.htm