is a SI
-multiple (see prefix tera
) of the unit byte
digital information storage
equal to 1012
( ) bytes or 1000 gigabytes
. The unit symbol for the terabyte is
The designation terabyte is rarely used to refer to the tebibyte
, its binary
analogue, because only recent (since 2007) disk drives
have this capacity. Disk drive sizes are always designated in SI
units by manufacturers. However, a possible confusion arises 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
(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
bytes, or 1024 gibibytes
leading to the following definitions:
- In standard SI usage, 1 terabyte (TB) equals = 10004
or 1012 bytes.
- Using the traditional binary interpretation, a terabyte is =
10244 = 240 bytes = 1 tebibyte (TiB).
The capacities of computer storage devices are typically specified
using their 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 decimal units.
Examples of terabyte usage
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 has claimed that "As of May 2009,
the Library has collected almost 100 terabytes of
- Online data bases - Ancestry.com claims approximately 600 TB
of genealogical data with the inclusion of US Census data from 1790
- Computer hardware - Hitachi
introduced the world's first one terabyte hard disk drive in
- Internet traffic - In 1993, total Internet traffic amounted to approx. 100 TB
for the year. , Cisco Systems
estimated Internet traffic at 160 TB/s (which assuming to be
statistically constant comes to 5 zettabytes for the year).
- Social networks - As of May 2009, Yahoo! Groups had
"40 terabytes of data to index"
- Video - Released in 2009, the 3D animated film
Monsters vs. Aliens
used 100 TB of storage during development.
- Usenet messages - In October of 2000, the Deja News
Usenet archive had stored over 500 million Usenet messages which used 1.5 TB of storage