The petabyte is a multiple of the unit byte for digital information. The prefix peta indicates the fifth power of 1000 and means 1015 in the International System of Units (SI), and therefore 1 petabyte is one quadrillion (short scale) bytes, or 1 billiard (long scale) bytes. The unit symbol for the petabyte is PB.
1 PB = 1000000000000000B = 1015bytes = 1000terabytes.
One thousand petabytes (1000 PB) is equal to one exabyte (1 EB).
Examples of the use of the petabyte to describe data sizes in different fields are:
- Telecommunications (capacity): The world's effective capacity to exchange information through two-way telecommunication networks was 281 petabytes of information in 1986, 471 petabytes in 1993, 2,200 petabytes in 2000, and 65,000 petabytes in 2007 (this is the informational equivalent to every person exchanging 6 newspapers per day).
- Telecommunications (usage): In 2008, AT&T transfers about 30 petabytes of data through its networks each day.
- Internet: Google processed about 24 petabytes of data per day in 2009. The BBC's iPlayer is reported to have transferred up to 7 petabytes each month in 2010. In 2012, Imgur transferred about 4 petabytes of data per month.
- The Wayback Machine, as of October 2016[update], has a total data of 15 petabytes.
- Supercomputers: In January 2012, Cray began construction of the Blue Waters, which has "up to 500 petabytes of tape storage".
- Data storage system: In August 2011, IBM was reported to have built the largest storage array ever, with a capacity of 120 petabytes.
- Databases: Teradata Database 12 has a capacity of 50 petabytes of compressed data.
- Data mining: In August 2012, Facebook's Hadoop clusters include the largest single HDFS cluster known, with more than 100 PB physical disk space in a single HDFS filesystem. Yahoo stores 2 petabytes of data on behavior.
- Digital archives: The Internet Archive surpassed 15 petabytes, as of May 2014[update].
- Email: In May 2013, Microsoft announces that as part of their migration of Hotmail accounts to the new Outlook.com email service, they migrated over 150 petabytes of user data in six weeks.
- File sharing (centralized): At its 2012 closure of file storage services, Megaupload held ~28 petabytes of user uploaded data.
- File sharing (peer-to-peer): 2013 - BitTorrent Sync has transferred over 30 petabytes of data since its pre-alpha release in January 2013.
- Film: The 2009 film Avatar is reported to have taken over 1 petabyte of local storage at Weta Digital for the rendering of the 3D CGI effects.
- Video streaming: As of May 2013[update], Netflix had 3.14 petabytes of video "master copies", which it compresses and converts into 100 different formats for streaming.
- Photos: As of January 2013[update], Facebook users had uploaded over 240 billion photos, with 350 million new photos every day. For each uploaded photo, Facebook generates and stores four images of different sizes, which translated to a total of 960 billion images and an estimated 357 petabytes of storage.
- Music: One petabyte of average MP3-encoded songs (for mobile, roughly one megabyte per minute), would require 2000 years to play.
- Games: As of 2009[update], World of Warcraft uses 1.3 petabytes of storage to maintain its game.
- Steam, a digital distribution service, delivers over 16 petabytes of content to American users weekly.
- Cloud backup: Multiple backup vendors, including Code42, Backblaze, and Mozy claim to store 90 or more petabytes of user backup data.
- Physics: The experiments in the Large Hadron Collider produce about 15 petabytes of data per year, which are distributed over the Worldwide LHC Computing Grid. In July 2012 it was revealed that CERN amassed about 200 petabytes of data from the more than 800 trillion collisions looking for the Higgs boson. The Large Hadron Collider is also able to produce 1 petabyte of data per second, but most of it is filtered out. 
- Neurology: It is estimated that the human brain's ability to store memories is equivalent to about 2.5 petabytes of binary data.
- Climate science: The German Climate Computing Centre (DKRZ) has a storage capacity of 60 petabytes of climate data.
- Folding@home (Scientific Data): Folding@home has generated 0.5 petabytes of simulated data.
- Google Photos had an estimated of 13.7 petabytes worth of photos uploaded in the first year of its existence.
- "The World's Technological Capacity to Store, Communicate, and Compute Information", Martin Hilbert and Priscila López (2011), Science (journal), 332(6025), 60-65; see also "free access to the study" and "video animation".
- "AT&T- News Room". Att.com. 23 October 2008. Retrieved 16 August 2009.
- "MapReduce". Portal.acm.org. Retrieved 16 August 2009.
- "Article". CNET UK. Retrieved 11 January 2010.
- "I created Imgur. AMA". Alan Schaaf. Retrieved 15 August 2012.
- Goel, Vinay (October 23, 2016). "Defining Web pages, Web sites and Web captures". Internet Archive Blogs. Retrieved 22 October 2017.
- "About Blue Waters".
- Simonite, Tom (25 August 2011). "IBM Builds Biggest Data Drive Ever". Technology Review. Retrieved 18 October 2011.
- "Teradata Database 12.0 - Database Management - SQL Database". Teradata.com. Retrieved 16 August 2009.
- Paul Rubens (20 September 2004). "Thanks for memory (but I need more)". BBC News.
Of course there's no such thing as a petabyte iPod, but the good news is that we may not have too long to wait for one. Hitachi Data Systems already sells a product called the TagmaStore Universal Storage Platform which can manage up to 32 petabytes of storage for the very largest corporations, so you'd have to conclude that a pocket-sized consumer version isn't out of the question in a decade or so.
- "Under the Hood: Hadoop Distributed Filesystem reliability with Namenode and Avatarnode". Facebook. Retrieved 14 April 2013.
- Lai, Eric. "Size matters: Yahoo claims 2-petabyte database is world's biggest, busiest". Computerworld. Retrieved 13 March 2013.
- Brownell, Brett (22 May 2014). "Meet the People Behind the Wayback Machine, One of Our Favorite Things About the Internet". Mother Jones. Retrieved 29 May 2014.
- "Outlook.com: 400 million active accounts, Hotmail upgrade complete and more features on the way".
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- Kane, Zee (1 January 2010). "Believe it or not: Avatar takes 1 petabyte of storage space". Thenextweb.com. Retrieved 14 January 2010.
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- Vance, Ashlee (9 May 2013). "Netflix, Reed Hastings Survive Missteps to Join Silicon Valley's Elite". Businessweek. Retrieved 22 May 2014.
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- Radd, David (18 September 2009). "Blizzard Drops World of Warcraft Stat Bomb". Industrygamers.com. Archived from the original on 22 September 2009. Retrieved 18 September 2009.
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- "Big Data Software Problem Behind CERN's Higgs Boson Hunt".
- "CERN Data Centre passes the 200-petabyte milestone". CERN. Retrieved 6 July 2017.
- Reber, Paul (2 April 2013). "What Is the Memory Capacity of the Human Brain?". Scientific American. Retrieved 14 April 2013.
- Wickman, Forrest (2012-04-24). "Your Brain's Technical Specs". Slate. ISSN 1091-2339. Retrieved 2017-03-31.
- Treehugger, 11 Dec 2009: Meet the world's most powerful weather supercomputer
- "Folding@home". 2011-02-02. Retrieved 2011-02-02.
- "Google Photos: One year, 200 million users, and a whole lot of selfies". Official Google Blog. Retrieved 2016-05-29.