| Megaoctets per second (Mo/s) | Exbioctets per second (Eio/s) |
|---|---|
| 1 Megaoctet per second | 8.67361737988 × 10-13 Eio/s |
| 2 Megaoctets per second | 1.73472347598 × 10-12 Eio/s |
| 3 Megaoctets per second | 2.60208521397 × 10-12 Eio/s |
| 4 Megaoctets per second | 3.46944695195 × 10-12 Eio/s |
| 5 Megaoctets per second | 4.33680868994 × 10-12 Eio/s |
| 10 Megaoctets per second | 8.67361737988 × 10-12 Eio/s |
| 20 Megaoctets per second | 1.73472347598 × 10-11 Eio/s |
| 25 Megaoctets per second | 2.16840434497 × 10-11 Eio/s |
| 50 Megaoctets per second | 4.33680868994 × 10-11 Eio/s |
| 100 Megaoctets per second | 8.67361737988 × 10-11 Eio/s |
| Reference | Megaoctets per second (Mo/s) | Exbioctets per second (Eio/s) |
|---|---|---|
| A dial-up modem | 0.007 Mo/s | 6.07153 × 10-15 Eio/s |
| Typical home broadband | 12.5 Mo/s | 1.0842 × 10-11 Eio/s |
| Gigabit Ethernet | 125 Mo/s | 1.0842 × 10-10 Eio/s |
| Streaming a 4K film | 3.125 Mo/s | 2.71051 × 10-12 Eio/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 exbioctet per second is a unit of data transfer rate equal to 1,024 pebioctets per second, or two to the sixtieth power octets per second. Its symbol is Eio/s. It is the binary counterpart of the exaoctet per second, and the two differ by 15.3 per cent.
No machine, network or aggregate reaches this rate. An exbioctet per second is more than eight times the total instantaneous traffic of the entire internet, and it would move the world's whole stock of stored data in a matter of minutes. The unit describes a capacity with no source that could supply it and no destination that could take it in.
Two to the sixtieth is nevertheless a familiar number in computing, because it is the size of the address space a 64-bit machine can reach in octets divided by sixteen. The same power of two turns up in filesystem limits, in memory maps and in the design of every system built on that architecture, so the quantity is well known even though no rate approaches it.
The unit exists because the IEC series was defined completely. Every binary prefix pairs with every unit, exactly as every metric prefix does, so that a reader who has never seen Eio/s can decode it from the prefix alone. A system with gaps would need a table of permitted combinations, which is precisely what a rule-based system exists to avoid.
The difference from the decimal unit is worth restating at each level because it compounds. At the kibioctet it was 2.4 per cent, here it is more than an eighth, and at the yobioctet it will be more than a fifth. That growth is the reason the binary prefixes were created, and it is why the lowercase i has to be written even in figures nobody will check.
For a converter, the treatment is mechanical: six multiplications by 1,024 from octets, or the equivalent divisions coming down. The value of doing it correctly is not that anyone will use the result, but that a tool which handles every case the same way can be trusted on the cases that matter.
One exbioctet per second equals 1,024 pebioctets per second, 1,152,921,504,606,846,976 octets per second, or about 1.153 exaoctets per second.