Conversion from Petaoctets per second to Mebioctets per second

Information about the Petaoctet per second (Po/s)

The petaoctet per second is a unit of data transfer rate equal to a thousand teraoctets per second, or eight petabits per second. Its symbol is Po/s. It describes the total internal bandwidth of the largest computing machines rather than any single connection, and it exists as an aggregate rather than as a rate anything can sustain on its own.

The clearest case is the interconnect of an exascale supercomputer. Such a machine has tens of thousands of nodes, each linked to the network at hundreds of gigaoctets per second, and the sum across the whole fabric reaches petaoctets per second. That figure is the reason such machines can run a single calculation spread over the whole system rather than many small independent ones.

Memory bandwidth adds up the same way. A machine with ten thousand accelerators, each with several teraoctets per second of local memory bandwidth, has tens of petaoctets per second in total. Whether that total means anything depends entirely on the calculation: a problem that can be divided so each node works mostly on its own data can use it, and a problem that cannot, cannot.

Data centre networks reach this range too. The aggregate capacity of the switching fabric inside a very large facility, counting every link between every rack, is measured in petaoctets per second. The design goal is that any server can reach any other at close to full speed, which requires far more internal capacity than the facility's external connections.

For scale, a petaoctet per second would transfer the entire contents of a large national archive in a second, or fill every hard drive manufactured in a day within about a minute. No storage system can supply data at this rate, and none can absorb it; the number describes movement inside a machine, between memory and processors, where nothing is being stored at all.

The unit also serves in optical research, where a single fibre carrying a petabit per second is 125 teraoctets per second, and an experimental system aggregating several such fibres approaches the petaoctet. Those figures come from laboratories rather than from anything deployed.

One petaoctet per second equals 1,000 teraoctets per second, 8 petabits per second, or about 0.8882 pebioctets per second.

Information about the Mebioctet per second (Mio/s)

The mebioctet per second is a unit of data transfer rate equal to 1,048,576 octets per second, which is 1,024 kibioctets per second. Its symbol is Mio/s. It is the unit that disc benchmarks, copy tools and backup programs report in, and one of the few binary units most people see regularly without noticing.

Storage measurement produces it naturally. A benchmark writes and reads blocks whose size is a power of two, times the operation, and divides. The result is a binary rate, and reporting it as such preserves the arithmetic. A tool that converted to decimal megaoctets would introduce a 4.9 per cent adjustment for no purpose other than to match a marketing convention.

That five per cent is exactly where the two conventions diverge visibly for consumers. A drive advertised at 550 megaoctets per second and measured at 524 mebioctets per second is performing precisely as claimed; the numbers differ only because one is decimal and the other binary. A great deal of complaint about storage performance is this arithmetic misread as a shortfall.

For everyday sizes, one mebioctet per second copies a photograph in three seconds and a two-gigaoctet film in about half an hour. Modern drives run hundreds or thousands of times faster, so the unit is now the resolution at which small differences are reported rather than the scale of the whole figure.

The unit also appears in memory and cache measurements, in database throughput reports and in the output of the low-level commands that write disc images. All of these count in binary blocks because the underlying structures are binary, and all of them report in mebioctets per second because that is what the count divided by the time actually gives.

The habit of writing the lowercase i is worth keeping. It costs one character and it tells a later reader which of two conventions produced the number, which is information that cannot be recovered from context once it has been left out.

One mebioctet per second equals 1,048,576 octets per second, 1,024 kibioctets per second, or about 1.049 megaoctets per second.