| Megaoctets per second (Mo/s) | Exabits per second (Ebit/s) |
|---|---|
| 1 Megaoctet per second | 8 × 10-12 Ebit/s |
| 2 Megaoctets per second | 1.6 × 10-11 Ebit/s |
| 3 Megaoctets per second | 2.4 × 10-11 Ebit/s |
| 4 Megaoctets per second | 3.2 × 10-11 Ebit/s |
| 5 Megaoctets per second | 4 × 10-11 Ebit/s |
| 10 Megaoctets per second | 8 × 10-11 Ebit/s |
| 20 Megaoctets per second | 1.6 × 10-10 Ebit/s |
| 25 Megaoctets per second | 2 × 10-10 Ebit/s |
| 50 Megaoctets per second | 4 × 10-10 Ebit/s |
| 100 Megaoctets per second | 8 × 10-10 Ebit/s |
| Reference | Megaoctets per second (Mo/s) | Exabits per second (Ebit/s) |
|---|---|---|
| A dial-up modem | 0.007 Mo/s | 5.6 × 10-14 Ebit/s |
| Typical home broadband | 12.5 Mo/s | 1 × 10-10 Ebit/s |
| Gigabit Ethernet | 125 Mo/s | 0.000000001 Ebit/s |
| Streaming a 4K film | 3.125 Mo/s | 2.5 × 10-11 Ebit/s |
The megaoctet per second is a unit of data transfer rate equal to one million octets per second, or eight megabits per second. Its symbol is Mo/s. It is the unit in which storage devices and their interfaces are rated, and the one a file manager shows while a copy is running.
Storage speeds fall naturally into this range. A mechanical hard drive sustains 100 to 250 megaoctets per second on sequential reads. A solid-state drive on the older interface reaches about 550, which is the limit of that interface rather than of the drive. A modern drive on the faster interface reaches several thousand, at which point the unit gives way to gigaoctets per second.
Interface speeds tell the same story from the other side. The successive versions of the universal serial bus have offered roughly 1.5, 60, 625 and 2,500 megaoctets per second at their nominal rates, and memory card standards have followed a similar path. A device is always limited by whichever of the two is slower, and matching them is the practical art of building a fast system.
For everyday sizes, one megaoctet per second transfers a photograph in a couple of seconds and a two-gigaoctet film in about half an hour. At 500 megaoctets per second the same film takes four seconds. That contrast explains why the perceived speed of a computer changed so completely when solid-state storage replaced mechanical drives, even though processors improved far less over the same period.
Sequential rates like these are the best case. Reading many small files instead of one large one costs far more, because each file requires locating its data and reading its record. A drive that sustains 500 megaoctets per second in sequence may manage only a few tens when copying a directory of thousands of small files, and that is where the difference between drive technologies is most visible.
The unit also describes the throughput of a busy network connection: a gigabit link delivers 125 megaoctets per second at best, so a fast local network and a fast drive are now comparable, and neither is obviously the limiting factor in a transfer.
One megaoctet per second equals 1,000,000 octets per second, 8 megabits per second, or about 0.9537 mebioctets per second.
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.