| Exbioctets (Eio) | Exaoctets (Eo) |
|---|---|
| 1 Exbioctet | 1.15292150461 Eo |
| 2 Exbioctets | 2.30584300921 Eo |
| 3 Exbioctets | 3.45876451382 Eo |
| 4 Exbioctets | 4.61168601843 Eo |
| 5 Exbioctets | 5.76460752303 Eo |
| 10 Exbioctets | 11.5292150461 Eo |
| 20 Exbioctets | 23.0584300921 Eo |
| 25 Exbioctets | 28.8230376152 Eo |
| 50 Exbioctets | 57.6460752303 Eo |
| 100 Exbioctets | 115.292150461 Eo |
| Reference | Exbioctets (Eio) | Exaoctets (Eo) |
|---|---|---|
| A plain text message (160 characters) | 1.38778 × 10-16 Eio | 1.6 × 10-16 Eo |
| A three-minute MP3 | 2.60209 × 10-12 Eio | 3 × 10-12 Eo |
| A smartphone photo | 3.46945 × 10-12 Eio | 4 × 10-12 Eo |
| A high-definition film | 0.00000000346945 Eio | 0.000000004 Eo |
| A dual-layer Blu-ray disc | 0.0000000433681 Eio | 0.00000005 Eo |
The exbioctet is a unit of digital information equal to two to the sixtieth power octets, which is 1,024 pebioctets. Its symbol is Eio. It is the binary counterpart of the exaoctet, and the two differ by 15.3 per cent.
One number involving this unit is quoted more than any other: sixteen exbioctets, the size of the address space a 64-bit processor can reach. Two to the sixty-fourth octets is 16 EiB, and that figure is the theoretical ceiling on the memory of every machine built on the architecture that has dominated computing since the mid-2000s.
The same limit reappears in filesystems. A filesystem that numbers its blocks with 64-bit values can address 16 exbioctets of blocks, and several modern designs state exactly that as their maximum volume size. Others state 8 exbioctets, having reserved one bit for a sign or a flag — a detail that halves the limit and is worth knowing when reading a specification.
Nothing approaches these sizes in practice. The largest storage systems in the world hold exaoctets, and the total of all data held by humanity is a few hundred zettaoctets, which is tens of thousands of exbioctets. The 64-bit ceiling was chosen precisely so that it would not be reached, and the transition from 32 bits, whose four-gibioctet limit was reached within a decade, is why the designers left so much room.
An exbioctet is 1,152,921,504,606,846,976 bits and 128 pebioctets. It is a quantity that exists in specifications, in address arithmetic and in the design documents of large systems, and nowhere else. Describing it in terms of photographs or films is not useful, because no collection of either comes close.
The symbol Eio and its decimal sibling Eo differ by more than an eighth, which is far too much to leave to inference. When a document writes EB in the context of an address space, it almost certainly means EiB, because address spaces are powers of two by construction; when it writes EB about stored data, it almost certainly means the decimal unit.
One exbioctet equals 1,024 pebioctets, 1,152,921,504,606,846,976 octets, 8 exbibits, or about 1.153 exaoctets.
The exaoctet is a unit of digital information equal to a thousand petaoctets, or a billion gigaoctets. Its symbol is Eo. It is the unit in which the world's data flows and stockpiles are counted, and it belongs to civilisations rather than to companies or machines.
The most quoted figure involving it is global internet traffic, which passed one exaoctet per month around 2004 and now runs to several hundred exaoctets monthly. Written as an annual total that is several thousand exaoctets, which is why the zettaoctet was pressed into service for yearly figures a decade ago.
A frequently repeated claim holds that all the words ever spoken by human beings would amount to about five exaoctets in text. The estimate comes from a 2003 study and is very rough, but it makes the point: five exaoctets is now less than a fortnight of internet traffic. Whatever the exact number, the flow of data through the network long ago overtook the total of everything humanity has ever said.
Storage at exaoctet scale exists only at the largest cloud providers, and even there it is spread across dozens of buildings on several continents. The annual production of all the world's hard drives and flash memory together is a few hundred exaoctets, so the exaoctet is also the natural unit for describing the output of an entire industry.
What is stored at this scale is mostly not what people imagine. Backups, replicas, logs, telemetry, machine learning training corpora and video kept for regulatory reasons dominate. Deliberately created human work — documents, photographs, recordings that someone chose to make and keep — is a small and shrinking fraction of the whole.
The prefix exa has been part of the metric system since 1975, adopted at the same conference as peta. At the time these were prefixes without applications, defined for completeness. The fact that both became working units of a commercial industry within thirty years is the clearest single measure of how quickly digital information grew.
One exaoctet equals 1,000 petaoctets, 1,000,000,000 gigaoctets, 8 exabits, or about 0.8674 exbioctets.