| Exabits per second (Ebit/s) | Petaoctets per second (Po/s) |
|---|---|
| 1 Exabit per second | 125 Po/s |
| 2 Exabits per second | 250 Po/s |
| 3 Exabits per second | 375 Po/s |
| 4 Exabits per second | 500 Po/s |
| 5 Exabits per second | 625 Po/s |
| 10 Exabits per second | 1250 Po/s |
| 20 Exabits per second | 2500 Po/s |
| 25 Exabits per second | 3125 Po/s |
| 50 Exabits per second | 6250 Po/s |
| 100 Exabits per second | 12500 Po/s |
| Reference | Exabits per second (Ebit/s) | Petaoctets per second (Po/s) |
|---|---|---|
| A dial-up modem | 5.6 × 10-14 Ebit/s | 7 × 10-12 Po/s |
| Typical home broadband | 1 × 10-10 Ebit/s | 0.0000000125 Po/s |
| Gigabit Ethernet | 0.000000001 Ebit/s | 0.000000125 Po/s |
| Streaming a 4K film | 2.5 × 10-11 Ebit/s | 0.000000003125 Po/s |
The exabit per second is a unit of data transfer rate equal to a thousand petabits per second. Its symbol is Ebit/s. No link, no cable and no exchange point runs at this rate; the unit describes the internet as a whole, or a large part of it, at a single instant.
Global internet traffic can be expressed this way. Worldwide traffic of several hundred exaoctets a month works out to roughly one exabit per second on average, and peak hours run higher. That figure is the sum of every packet moving on every network on the planet, and it is the only quantity anyone routinely describes at this scale.
An exabit per second is 125 petaoctets per second. Nothing generates data at that rate in one place; the number is an aggregate of billions of separate flows, most of them tiny. A single video stream is a few megabits per second, so an exabit per second is on the order of a hundred million such streams running at once.
The composition of that traffic is dominated by video. Streaming services account for the largest share, followed by social platforms, software updates and cloud synchronisation. Ordinary web browsing and messaging, which people think of as the internet, are a small fraction of the total by volume even though they occupy most of the attention.
The unit also appears in projections of aggregate capacity. The total installed capacity of all submarine cables, if every wavelength on every fibre pair were lit and used simultaneously, is in the exabit-per-second range. Actual utilisation is far below that, because capacity is built ahead of demand and because routes must carry each other's traffic when a cable fails.
The prefix exa is a thousand to the sixth power. It was adopted in 1975, when nobody expected it to describe anything but astronomical quantities, and it now describes the working throughput of a communications system built by human beings. The interval between definition and everyday use was about forty years.
One exabit per second equals 1,000 petabits per second, 125 petaoctets per second, or about 0.8674 exbibits per second.
The petaoctet per second is a unit of data transfer rate equal to a thousand teraoctets per second, or eight petabits per second. Its symbol is Po/s. It describes the total internal bandwidth of the largest computing machines rather than any single connection, and it exists as an aggregate rather than as a rate anything can sustain on its own.
The clearest case is the interconnect of an exascale supercomputer. Such a machine has tens of thousands of nodes, each linked to the network at hundreds of gigaoctets per second, and the sum across the whole fabric reaches petaoctets per second. That figure is the reason such machines can run a single calculation spread over the whole system rather than many small independent ones.
Memory bandwidth adds up the same way. A machine with ten thousand accelerators, each with several teraoctets per second of local memory bandwidth, has tens of petaoctets per second in total. Whether that total means anything depends entirely on the calculation: a problem that can be divided so each node works mostly on its own data can use it, and a problem that cannot, cannot.
Data centre networks reach this range too. The aggregate capacity of the switching fabric inside a very large facility, counting every link between every rack, is measured in petaoctets per second. The design goal is that any server can reach any other at close to full speed, which requires far more internal capacity than the facility's external connections.
For scale, a petaoctet per second would transfer the entire contents of a large national archive in a second, or fill every hard drive manufactured in a day within about a minute. No storage system can supply data at this rate, and none can absorb it; the number describes movement inside a machine, between memory and processors, where nothing is being stored at all.
The unit also serves in optical research, where a single fibre carrying a petabit per second is 125 teraoctets per second, and an experimental system aggregating several such fibres approaches the petaoctet. Those figures come from laboratories rather than from anything deployed.
One petaoctet per second equals 1,000 teraoctets per second, 8 petabits per second, or about 0.8882 pebioctets per second.