Definition

Terabyte (TB)

Contributor(s): Erin Sullivan, Brien Posey and Jack Duffie

A Terabyte (TB) is a measure of computer storage capacity that is approximately 2 to the 40th power, or 10 to the 12th power, which equals approximately a trillion bytes. A Terabyte is more precisely defined as 1,024 gigabytes (GB), while a petabyte consists of 1,024 TB.

The prefix Tera is derived from the Greek word for monster. It would take 728,177 floppy disks or 1,498 CDs to hold one TB of information. However, thanks to modern technology, the average computer hard drive now has more than 1 TB of hard disk drive (HDD) capacity.

Since a Terabyte generally refers to approximately one trillion bytes, the term tebibyte (TiB) was coined. A tebibyte refers to 1,099,511,627,776 bytes, exactly 2 to the 40th power. Unless the exact number of bytes is needed, Terabyte is the accepted unit of measurement.

History

Hitachi began selling 1 TB HDDs to consumers in 2007. Prior to that, HDDs were relatively small and expensive.

For example, when the IBM Personal Computer XT -- the successor to the original IBM PC -- was released in 1983, it was the first PC to include a built-in hard drive as a standard feature. At the time, HDDs were available in 10 megabyte (MB) or 20 MB capacities. It was not until 1991 that 1 GB disks were available to consumers, and even then a gigabyte of storage cost nearly $3,000.

The first 1 TB HDD marked a milestone for data storage, and it also emphasized how rapidly storage capacity was growing. With the drive's release, Hitachi noted that it took 35 years for the storage industry to reach 1 GB and 14 years to increase that to 500 GB. After that, it took a mere two years to reach 1 TB.

Hitachi quickly gained competition. In 2008, Seagate released the FreeAgent GoFlex portable drive, which offered 1.5 TB of storage. Today, HDDs such as the Seagate Exos drive are available with 12 TB to 14 TB of storage. Solid-state drives (SSDs) can hold up to 100 TB of storage.

Seagate Exos HDDs can currently hold up to 14 Terabytes.
Seagate Exos HDDs can currently hold up to 14 Terabytes.

Visualizing a Terabyte

According to futurist Ray Kurzweil in The Singularity is Near, the capacity of a human being's functional memory is estimated to be 1.25 TB. Here are some less abstract examples of what a 1 Terabyte drive can hold:

  • 472 hours of broadcast-quality video;
  • 130,000 digital photos;
  • 150 hours of high-definition recording; and
  • 2,000 hours of CD-quality recording.

According to NASA, the Hubble Space Telescope has an archive of 150 TB and generates approximately 10 TB of new data a year.

Terabyte vs. other data storage values

Major vendors with Terabyte storage

A series of mergers of HDD vendors in the early 2000s left Seagate, Toshiba and Western Digital -- which now owns Hitachi -- as the main companies that sell HDDs with a TB or more of capacity. Vendors that sell SSDs with at least 1 TB of capacity include Intel, Micron Technology, Kingston Technology, Samsung, Toshiba and Western Digital/SanDisk.

The advent of helium-filled HDDs has enabled storage drives to use the lightness of helium to increase storage density. First offered by HGST in 2013, helium-filled drives make up some of the highest capacity Terabyte drives available. In 2017, Western Digital released a 12 TB helium-based HDD, the Ultrastar He12.

Other technologies, such as Seagate's Heat-Assisted Magnetic Recording (HAMR) and Western Digital's Microwave-Assisted Magnetic Recording (MAMR), increase drive density and enable more TBs to fit on a single HDD.

As high-capacity flash storage takes its place in the data storage market, enterprise SSD vendors are offering even more Terabytes, with Nimbus Data announcing a 100 TB SSD in March 2018. The Nimbus SATA-based ExaDrive 100 TB SSD is estimated to cost 50 cents to 90 cents per GB or, on the low end, at least $50,000.

The cost of a Terabyte HDD

Like any other computer component, the cost of HDDs has decreased over time. When 1 TB HDDs were first introduced in 2007, a consumer-grade drive cost approximately $375. By mid-2018, a 4 TB external hard drive for consumers cost approximately $150. This worked out to four times the capacity for less than half the 2007 cost. Eight Terabyte drives in 2018 cost about $600, with some archive-grade drives available for as little as $300.

When it comes to cost per GB, TB-level HDDs can get interesting. With Seagate, for example, 1 TB to 4 TB consumer drives decrease in cost per gigabyte as they increase in capacity, with 1 TB drives priced at $.050 per GB ($49.99 for the drive) and 4 TB drives at $.025 per GB ($99.99 for the drive). After that, prices increase significantly to $240.00 for a 6 TB drive ($0.40/GB) and $307.34 for 8 TB ($0.038/GB).

The per-GB cost is lower for larger capacity drives. Seagate 10 TB drives are $339.00, while the vendor's 12 TB drives cost $472.00.

Cloud storage can also be sold in Terabyte increments, usually priced per month. Cloud storage providers such as Dropbox, Google and OneDrive offer 1 TB of storage from $6.99 to $9.99 per month. Terabyte-level storage is available on SSDs, as well, but at a much higher price. For example, a 1 TB SSD from Samsung starts at $429.99.

This was last updated in June 2018

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I need more information about terabyte HDD.
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What new technologies do you think will help to increase the areal density of drives and catapult them into triple-digit terabyte drives?
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This article should have included the distinction that ALL hard drives are not measured in binary terabytes, but in a rounded (eg trillion bytes). So a "1 TB" hard drive is actually 0.931 TB as the computer would report it. Annoyed techies came up with a new definition to be very clear they are talking about base 2 byte amounts. It is denoted as TiB or terabyte. If you see that then you know for sure it's 1024GB, otherwise there is no guarantee which it is.
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I'm incredibly impressed with the amount of storage I can carry in my hand; equally so with the incredible drop in cost. Nice. Win/win.

Yet programs grow fatter and the drives fill faster. My first digital camera delivered astonishingly huge 1MB files. Now, my little carry-around churns out 10MB pictures and the pros around me snap 30 and 40 and 50MB photos. A few of those fill a drive quickly.

While storage space and the data to be stored have a history of leapfrogging each other, what's next...? Do I keep getting bigger drives in smaller spaces? Or is there some new technology on the horizon...?
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$600? I see a $250 one from Seagate. http://www.engadget.com/2014/12/12/seagate-ships-8tb-shingled-hard-drive/
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