| Mebibits per second (Mibit/s) | Pebioctets per second (Pio/s) |
|---|---|
| 1 Mebibit per second | 1.16415321827 × 10-10 Pio/s |
| 2 Mebibits per second | 2.32830643654 × 10-10 Pio/s |
| 3 Mebibits per second | 3.49245965481 × 10-10 Pio/s |
| 4 Mebibits per second | 4.65661287308 × 10-10 Pio/s |
| 5 Mebibits per second | 5.82076609135 × 10-10 Pio/s |
| 10 Mebibits per second | 0.00000000116415321827 Pio/s |
| 20 Mebibits per second | 0.00000000232830643654 Pio/s |
| 25 Mebibits per second | 0.00000000291038304567 Pio/s |
| 50 Mebibits per second | 0.00000000582076609135 Pio/s |
| 100 Mebibits per second | 0.0000000116415321827 Pio/s |
| Reference | Mebibits per second (Mibit/s) | Pebioctets per second (Pio/s) |
|---|---|---|
| A dial-up modem | 0.0534058 Mibit/s | 6.21725 × 10-12 Pio/s |
| Typical home broadband | 95.3674 Mibit/s | 0.0000000111022 Pio/s |
| Gigabit Ethernet | 953.674 Mibit/s | 0.000000111022 Pio/s |
| Streaming a 4K film | 23.8419 Mibit/s | 0.00000000277556 Pio/s |
The mebibit per second is a unit of data transfer rate equal to 1,048,576 bits per second. Its symbol is Mibit/s. It is the binary counterpart of the megabit per second, and the two differ by 4.9 per cent — small, but large enough to change a headline figure.
That five per cent is where the unit starts to matter. A connection advertised at 100 megabits per second and a connection at 100 mebibits per second differ by about five megabits, which is a whole high-definition video stream. In a specification, a contract or a benchmark report, quoting one and delivering the other is a real discrepancy rather than a rounding difference.
In practice the confusion is rare in networking, because network equipment is always specified in decimal. What produces mebibit figures is measurement software: a tool that counts a transfer in mebioctets and divides by elapsed seconds is reporting a binary rate, and multiplying by eight makes it mebibits per second. A person comparing that reading with an advertised rate must convert twice, once for the base and once for the factor of eight.
Where a genuine binary rate does arise is inside a machine. A memory bus transfers a fixed number of bits per clock cycle, and the width is a power of two — sixty-four bits at a time, for instance — so the quantity moved per cycle is binary even though the clock frequency is not. Rates derived from such a structure are naturally expressed with binary prefixes.
For scale, a mebibit per second is 131,072 octets per second, or about 128 kibioctets per second. That is roughly a photograph every two seconds, or a plain-text novel every four. It is a rate at which the modern web is slow but usable, which puts it in the range that mobile networks fall to when congested.
The correct symbol has the lowercase i, and its presence is the only reliable way to tell the two conventions apart. A document writing Mbit/s in a context where the underlying figure came from a binary computation has misstated its own measurement by five per cent.
One mebibit per second equals 1,048,576 bits per second, 131,072 octets per second, or about 1.049 megabits per second.
The pebioctet per second is a unit of data transfer rate equal to 1,024 tebioctets per second, or two to the fiftieth power octets per second. Its symbol is Pio/s. It is the binary counterpart of the petaoctet per second, and the two differ by 12.6 per cent.
The rate exists only as a total. The aggregate memory bandwidth of a whole supercomputer, or the summed capacity of the network fabric joining its cabinets, reaches this range, and both are sums over tens of thousands of components, each of which moves a few hundred gibioctets per second on its own.
Whether such a total means anything depends on the calculation being run. A problem that divides so that each node works mostly on its own data can use the full aggregate. A problem where every node must constantly consult every other cannot, and the machine's effective bandwidth falls to what the slowest shared path allows. Most of the art of parallel programming lies in getting problems into the first category.
In octets a pebioctet per second is 1,125,899,906,842,624, and in decimal terms about 1.126 petaoctets per second. The 12.6 per cent difference is the accumulated effect of five multiplications by 1.024, and it is now large enough that no report can leave the convention unstated without introducing real uncertainty.
The unit also appears in descriptions of parallel filesystems at the largest facilities, where a storage system spread across tens of thousands of drives delivers a few pebioctets per second to a compute cluster. That number determines how quickly the machine can checkpoint its state, which in turn determines how much work is lost when a component fails — and in a machine of that size, something is always failing.
For a converter the requirement is simply that the arithmetic be exact and the label preserved. Multiplying by 1,024 five times is not difficult; silently substituting the decimal prefix is the error to avoid.
One pebioctet per second equals 1,024 tebioctets per second, 1,125,899,906,842,624 octets per second, or about 1.126 petaoctets per second.