# Petabyte

A petabyte is 1015 bytes of digital information. The unit symbol for the petabyte is PB. It is a measure of memory or data storage capacity.

## How much is a petabyte?

There are 1,024 terabytes (TB) or approximately 1 million gigabytes (GB) in a petabyte. 1,024 petabytes make up one exabyte. A petabyte is not suited for traditional data backups. To get an idea of how large a petabyte of storage is, here are some examples:

• A typical DVD holds 4.7 GB of data, meaning a PB of storage could hold 223,101 DVD-quality movies.
• To store one PB of data, 745 million floppy disks would be needed.
• The Library of Congress holds over 20 petabytes of data.
• A petabyte’s worth of data stored in 1GB flash drives would stretch over 92 football fields.

For comparison, this chart details a petabyte’s place in storage capacity.

## Petabytes and Pebibytes

A petabyte is sometimes defined as a 250 bytes. There are two different systems of measuring bytes: the Base10 SI system (SI) and the Base2 IEC (IEC) system. While 250 bytes is close to 1015, it is higher and has a different term pebibyte (PiB).

Computing is based on the binary system rather than decimal. At low levels, the SI and IEC terms are interchangeable. 103 = 1,000 and 210 = 1,024, so there is only slightly more than a 2 percent difference between the one kilobyte (1,000 bytes) and one kibibyte (1024 bytes). As storage systems are never run within 2 percent of their capacity, there is no operational difference between the two.

There is greater divergence, however, as we get into higher orders of magnitude. As shown in the table below, the percentage difference grows as the byte amount grows. Therefore, when specifying capacity of a large-scale system, it’s important not to combine the two different systems of counting data storage space.

 SI decimal prefixes IEC binary prefixes Percentage Difference IEC/SI Name Value Name Value kilobyte (kB) 103 kibibyte (KiB) 210 2.4% megabyte (MB) 106 mebibyte (MiB) 220 4.9% gigabyte (GB) 109 gibibyte (GiB) 230 7.4% terabyte (TB) 1012 tebibyte (TiB) 240 10.0% petabyte (PB) 1015 pebibyte (PiB) 250 12.6% exabyte (EB) 1018 exbibyte (EiB) 260 15.3% zettabyte (ZB) 1021 zebibyte (ZiB) 270 18.1% yottabyte (YB) 1024 yobibyte (YiB) 280 20.9%

## Petabyte storage vendors

As cloud computing as grown, enterprise increasingly needs storage ranging into the petabyte range. Storage vendors have scaled up to meet those needs by offering multi-petabyte rack servers. To learn more about rack server vendors who can deliver petabyte-plus-sized storage solutions in ServerWatch‘s Top Rack Servers product comparison.

Vangie Beal
Vangie Beal is a freelance business and technology writer covering Internet technologies and online business since the late '90s.

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