Conversion from Megaoctets per second to Terabits per second

Information about the Megaoctet per second (Mo/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.

Information about the Terabit per second (Tbit/s)

The terabit per second is a unit of data transfer rate equal to a thousand gigabits per second. Its symbol is Tbit/s. It is the unit of the internet's backbone: the submarine cables, the exchange points and the long-haul optical links that carry traffic between continents.

A single modern transoceanic cable carries several hundred terabits per second. It achieves this not with one enormous channel but with wavelength division multiplexing, which sends dozens of separate colours of light down each fibre at once, and with several fibre pairs in the same cable. Each wavelength carries a few hundred gigabits, and the totals add up.

The historical comparison is worth stating plainly. The first transatlantic telephone cable, laid in 1956, carried thirty-six simultaneous voice calls. A cable laid in the 2020s carries hundreds of terabits per second, enough for hundreds of millions of simultaneous calls. That is a factor of roughly ten million in seventy years, and it was achieved almost entirely by changing what is sent down the glass rather than by laying more cable.

Internet exchange points, where networks meet and hand traffic to one another, publish their throughput in terabits per second. The largest in Europe and Asia peak in the tens of terabits, and those public graphs are among the most reliable measurements of how heavily the internet is being used at a given moment, because they count real traffic rather than capacity.

In octets, a terabit per second is 125 gigaoctets per second — the contents of a large laptop's disc moved every second, continuously. No single storage system can feed such a link; the traffic on these routes is the aggregate of millions of separate connections, each of them tiny by comparison.

Laboratory records go far higher, into petabits per second, using multi-core fibre and hundreds of wavelengths at once, though over short distances under controlled conditions. The gap between what is demonstrated in a laboratory and what is deployed under an ocean has historically been about a decade.

One terabit per second equals 1,000 gigabits per second, 125 gigaoctets per second, or about 0.9095 tebibits per second.