Exabyte

The exabyte is a multiple of the unit byte for digital information. The prefix exa indicates multiplication by the sixth power of 1000 (10¹⁸) in the International System of Units (SI). Therefore, one exabyte is one quintillion bytes (short scale). The symbol for the exabyte is EB.

1 EB = 1000⁶bytes = 10¹⁸bytes = 1000000000000000000B = 1000 petabytes = 1millionterabytes = 1billiongigabytes.

A related unit, the exbibyte, using a binary prefix, is equal to 1024⁶ (=2⁶⁰)bytes, about 15% larger.

Usage examples and size comparisons

• A processor with a 64-bit address bus can address 16 exbibytes of memory,^[1] which is over 18 exabytes.
• The world's technological capacity to store information grew from 2.6 ("optimally compressed") exabytes in 1986 to 15.8 in 1993, over 54.5 in 2000, and to 295 (optimally compressed) exabytes in 2007. This is equivalent to less than one CD (650 MB) per person in 1986 (539 MB per person), roughly four in 1993, 12 in 2000, and almost 61 in 2007. Piling up the imagined 404 billion CDs from 2007 would create a stack from the earth to the moon and a quarter of this distance beyond (with 1.2 mm thickness per CD).^[2]
• The world's technological capacity to receive information through one-way broadcast networks was 432 exabytes of information in 1986, 715 exabytes in 1993, 1,200 exabytes in 2000, and 1,900 in 2007 (and with all the preceding examples assuming that those figures represent "optimally compressed" data).^[2]
• The world's effective capacity to exchange information through two-way telecommunication networks was 0.281 exabytes of information in 1986, 0.471 in 1993, 2.2 in 2000, and 65 exabytes in 2007 (yet again, all such amounts listed are strictly working off the basis that the data was in an "optimally compressed" form).^[2]
• In 2004, the global monthly Internet traffic passed 1 exabyte for the first time. In January 2007, Bret Swanson of the Discovery Institute coined the term exaflood for a supposedly impending flood of exabytes that would cause the Internet's congestive collapse.^[3][4] Nevertheless, the global Internet traffic has continued its exponential growth, undisturbed, and as of March 2010 it is estimated at 21 exabytes per month.^[5]
• The global data volume at the end of 2009 had reached 800 exabytes.^[6]
• According to an International Data Corporation paper sponsored by EMC Corporation, 161 exabytes of data were created in 2006, "3 million times the amount of information contained in all the books ever written", with the number expected to hit 988 exabytes in 2010.^[7][8][9]
• A gram of DNA can theoretically hold 455 exabytes.^[10]
• According to the CSIRO, in the next decade, astronomers expect to be processing 10 petabytes of data every hour from the Square Kilometre Array (SKA) telescope.^[11] The array is thus expected to generate approximately one exabyte every four days of operation. According to IBM, the new SKA telescope initiative will generate over an exabyte of data every day. IBM is designing hardware to process this information.^[12]
• According to the Digital Britain Report, 494 exabytes of data was transferred across the globe on June 15, 2009.^[13]
• Several filesystems use disk formats that support theoretical volume sizes of several exabytes, including Btrfs, XFS, ZFS, exFAT, NTFS, HFS Plus, and ReFS.
• The ext4 file system format supports volumes up to 1.1529215 exabytes in size, although the userspace tools cannot yet administer such filesystems.
• Oracle Corporation claimed the first exabyte tape library with the SL8500 and the T10000C tape drive in January 2011.^[14]

All words ever spoken

Allegedly, "all words ever spoken by human beings" could be stored in approximately 5 exabytes of data.^[15][16][17] This claim often cites a project at the UC Berkeley School of Information in support (although this project is now outdated and therefore not entirely accurate).^[18] The 2003 University of California Berkeley report credits the estimate to the website of Caltech researcher Roy Williams, where the statement can be found as early as May 1999.^[19] This statement has been criticized.^[20][21] Mark Liberman calculated the storage requirements for all human speech at 42 zettabytes (42,000 exabytes, and 8,400 times the original estimate), if digitized as 16 kHz 16-bit audio, although he did freely confess that "maybe the authors [of the exabyte estimate] were thinking about text".^[22]

Earlier studies from the University of California, Berkeley, estimated that by the end of 1999, the sum of human-produced information (including all audio, video recordings, and text/books) was about 12 exabytes of data.^[23] The 2003 Berkeley report stated that in 2002 alone, "telephone calls worldwide on both landlines and mobile phones contained 17.3 exabytes of new information if stored in digital form" and that "it would take 9.25 exabytes of storage to hold all U.S. [telephone] calls each year".^[18] International Data Corporation estimates that approximately 160 exabytes of digital information were created, captured, and replicated worldwide in 2006.^[24] Research from University of Southern California estimates that the amount of data stored in the world by 2007 was 295 exabytes and the amount of information shared on two-way communications technology, such as cell phones in 2007 as 65 exabytes.^[25][26]

Library of Congress

The content of the Library of Congress is commonly estimated to hold 10 terabytes of data in all printed material. Recent estimates of the size including audio, video, and digital materials start at 3 petabytes^[27] to 20 petabytes. Therefore, one exabyte could hold a hundred thousand times the printed material, or 500 to 3000 times all content of the Library of Congress.

Google

In 2013, Randall Munroe compiled published assertions about Google's data centers, and estimated that the company has about 10 exabytes stored on disk, and additionally approximately 5 exabytes on tape backup.^[28] The company has refused to comment on Munroe's estimate.^[29]

See also

• Orders of magnitude (data)

References