Petabyte

A petabyte is a unit of measurement in computers of approximately one thousand million million (American quadrillion) bytes.

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

1. 1,125,899,906,842,624 bytes - 1024 times 1024 times 1024 times 1024 times 1024, or 2⁵⁰. This is 1024 times a terabyte. This is the definition used in computer science and computer programming
2. 1,000,000,000,000,000 bytes - or 10 ¹⁵.

An exabyte is 1024 times a petabyte.

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

To clarify the meaning (1) above, 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." Thus meaning (1) is called by the IEC a pebibyte[?] (PiB), and meaning (2) is called by the IEC a petabyte. This naming convention has not, as of 2003, been widely adopted.

links: http://www.quinion.com/words/turnsofphrase/tp-kib1.htm

http://www.nist.gov/public_affairs/techbeat/tb9903.htm