| Megaoctets per second (Mo/s) | Zebibits per second (Zibit/s) |
|---|---|
| 1 Megaoctet per second | 6.77626357803 × 10-15 Zibit/s |
| 2 Megaoctets per second | 1.35525271561 × 10-14 Zibit/s |
| 3 Megaoctets per second | 2.03287907341 × 10-14 Zibit/s |
| 4 Megaoctets per second | 2.71050543121 × 10-14 Zibit/s |
| 5 Megaoctets per second | 3.38813178902 × 10-14 Zibit/s |
| 10 Megaoctets per second | 6.77626357803 × 10-14 Zibit/s |
| 20 Megaoctets per second | 1.35525271561 × 10-13 Zibit/s |
| 25 Megaoctets per second | 1.69406589451 × 10-13 Zibit/s |
| 50 Megaoctets per second | 3.38813178902 × 10-13 Zibit/s |
| 100 Megaoctets per second | 6.77626357803 × 10-13 Zibit/s |
| Reference | Megaoctets per second (Mo/s) | Zebibits per second (Zibit/s) |
|---|---|---|
| A dial-up modem | 0.007 Mo/s | 4.74338 × 10-17 Zibit/s |
| Typical home broadband | 12.5 Mo/s | 8.47033 × 10-14 Zibit/s |
| Gigabit Ethernet | 125 Mo/s | 8.47033 × 10-13 Zibit/s |
| Streaming a 4K film | 3.125 Mo/s | 2.11758 × 10-14 Zibit/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 zebibit per second is a unit of data transfer rate equal to two to the seventieth power bits per second, which is 1,024 exbibits per second. Its symbol is Zibit/s. It is the binary counterpart of the zettabit per second, and the two differ by 18.1 per cent — approaching a fifth.
Nothing runs at this rate, and nothing is designed to. A zebibit per second is about a thousand times the total instantaneous traffic of the internet, and it would move the world's entire stock of stored data in a matter of minutes. The unit exists because the IEC series, like the metric series it parallels, was defined completely rather than only as far as anyone then needed.
That completeness is a deliberate design principle rather than an oversight. A measurement system whose names run out at some arbitrary point forces every future user to improvise an extension, and improvised extensions conflict with one another. Defining the whole ladder in advance costs nothing and removes the possibility.
The eighteen per cent gap at this level is the clearest illustration of why the binary series was needed at all. At the kibibit the two conventions differed by 2.4 per cent, which nobody noticed; the discrepancy multiplies by 1.024 at each step, and by here it is large enough that no reader could treat the two labels as interchangeable even in casual writing.
In octets a zebibit per second is 147,573,952,589,676,412,928, or 128 exbioctets per second. Expressing the same rate in every unit on the scale is an exercise rather than an application, but it is one a converter has to perform correctly, because the arithmetic does not become approximate when the quantity becomes unreachable.
The practical lesson is the one the whole binary series teaches: the lowercase i is not optional. It is the only mark in a written figure that distinguishes a power of two from a power of ten, and by this point in the scale the two are nearly a fifth apart.
One zebibit per second equals 1,024 exbibits per second, 147,573,952,589,676,412,928 octets per second, or about 1.181 zettabits per second.