What are petabytes and just how big are they?

Enterprise storage is moving from tera to peta, but what do the terms mean?

Numbers against dark background

As the amount of data produced by businesses is constantly increasing, so is the demand for more data storage. That is why large measurement concepts that once might have seemed purely hypothetical, such as yottabytes, are now considered not too from reality after all.

Such is the case with petabytes. At one quadrillion bytes, saying that they contain quite a bit of data might be an understatement. In fact, the amount is rarely even considered by the average consumer, who will likely never need that much storage in their lifetime.

As such, petabyte-scale equipment is usually found in enterprise-grade infrastructure, or storage modules for large data centres. It is also often used by research institutions and large universities, even financial and pharmaceutical organisations.

Even if your data needs are not on that scale, it is worth getting to grips with the idea of petabyte storage, as it could become more mainstream in the future.

Mega, giga, tera... what's the difference?

Every measurement of storage is made up of bytes and each byte is made up of 8 bits, right at the bottom of the storage pile. From byte, we move up the size ladder, with kilobyte next in line, followed by megabyte, gigabyte, terabyte, petabyte, exabyte, and the unfathomably large zettabyte and yottabyte.

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In order to convert from a lower metric to a higher, the rule is to multiply the number by 1,024 - so 1 terabyte is the same as 1,024 gigabytes.

So for example: 1 GB = 1,024 MB = 1,048,576 KB = 1,073,741,824 B.

That may sound strange if you've always been told that a kilobyte was a thousand bytes, and a megabyte a thousand kilobytes. The confusion is in part due to the use of binary in computers instead of decimal - 1,000 would be 1111101000 in binary, which isn't a convenient group size to use for a storage metric.

The use of 'kilo' is also confusing, given that a kilometre is 1,000 metres, not 1,024. In fact, in 1998 the International Electrotechnical Commission introduced new standardised prefixes, including "kibibytes" instead of kilobytes and "mebibytes" instead of megabytes... but they never quite caught on.

Here's a comparison between the various sizes:

MetricExponentSize (bytes)
Byte (B)11
Kilobyte (KB)1024^11,024
Megabyte (MB)1024^21,048,576
Gigabyte (GB)1024^31,073,741,824
Terabyte (TB)1024^41,099,511,627,776
Petabyte (PB)1024^51,125,899,906,842,624
Exabyte (EB)1024^61,152,921,504,606,846,976
Zettabyte (ZB)1024^71,180,591,620,717,411,303,424
Yottabyte (YB)1024^81,208,925,819,614,629,174,706,176
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