Conversion from 10 Tebibits per second to Octets per second

Information about the Tebibit per second (Tibit/s)

The tebibit per second is a unit of data transfer rate equal to 1,099,511,627,776 bits per second, which is 1,024 gibibits per second. Its symbol is Tibit/s. It is the binary counterpart of the terabit per second, and the two differ by 10 per cent.

Ten per cent is the point at which the distinction becomes a matter of money rather than of pedantry. A supplier quoting a system at a hundred terabits per second and a customer measuring a hundred tebibits per second are not describing the same performance, and the difference is ten terabits — more than most organisations' entire external connectivity.

The rate belongs to the interior of very large machines. The aggregate memory bandwidth of a rack of accelerators, or the internal switching capacity of a large network chip, reaches this range, and both are built from power-of-two structures: memory channels of fixed binary width, switch ports in powers of two, buffers sized in binary. Expressing their totals with binary prefixes preserves the arithmetic that produced them.

In octets a tebibit per second is 137,438,953,472, or 128 gibioctets per second. That is more than any single storage device can supply and more than any external cable carries. It is a figure that describes something happening inside a cabinet, between chips connected by short traces on a board, where the physical distance is measured in centimetres.

Optical research also brushes this range. A laboratory demonstration carrying a petabit per second down one fibre is a thousand times higher, but individual wavelength channels and the electronics driving them work at tebibit-scale aggregates, and papers reporting them often state the binary figure because the underlying frame sizes are binary.

The habit of writing the lowercase i is worth keeping even where the reader is unlikely to check. A number written unambiguously can be converted correctly by anyone who reads it later; one written ambiguously cannot be repaired, and at ten per cent the ambiguity is no longer harmless.

One tebibit per second equals 1,024 gibibits per second, 137,438,953,472 octets per second, or about 1.100 terabits per second.

Information about the Octet per second (octet/s)

The octet per second is a unit of data transfer rate equal to eight bits per second. Its symbol is octet/s. It is the unit in which software reports transfer speeds, as against the bits per second in which hardware and network services advertise them, and the factor of eight between the two conventions is the source of endless confusion.

The division of labour is consistent once it is understood. Anything describing a physical link — an Ethernet port, a fibre connection, a radio channel, a broadband package — is quoted in bits per second, because bits are what the signalling actually carries. Anything describing a file moving from one place to another is quoted in octets per second, because files are measured in octets.

A download manager that reports 12 megaoctets per second on a connection sold as 100 megabits per second is not disagreeing with the advertisement; it is stating the same rate in the other convention, and the arithmetic between them is a division by eight. Recognising this immediately removes the most common cause of complaint about internet speed.

Individual octets per second appear in the same narrow places as individual bits: deep-space telemetry, low-power sensor links, and the slowest legacy serial connections. A rate of a hundred octets per second would move a page of text in about twenty seconds, which was a normal experience in the 1970s and is unimaginable now.

The unit also underlies the way disc and interface throughput is described. A drive that sustains 500 megaoctets per second is moving four gigabits per second across its interface, and matching the two figures is a routine part of system design: an interface rated in gigabits must be compared with a drive rated in octets, and the factor of eight decides whether one starves the other.

Storage tools reinforce the convention. Every file copy utility, backup program and command-line transfer tool reports in octets per second or its multiples, and every network measurement tool reports in bits per second. A person reading both at once has to keep the conversion in mind, which is exactly what makes the distinction worth stating explicitly.

One octet per second equals 8 bits per second, 0.008 kilobits per second, or 0.001 kilooctets per second.