| Petaoctets (Po) | Terabits (Tbit) |
|---|---|
| 1 Petaoctet | 8000 Tbit |
| 2 Petaoctets | 16000 Tbit |
| 3 Petaoctets | 24000 Tbit |
| 4 Petaoctets | 32000 Tbit |
| 5 Petaoctets | 40000 Tbit |
| 10 Petaoctets | 80000 Tbit |
| 20 Petaoctets | 160000 Tbit |
| 25 Petaoctets | 200000 Tbit |
| 50 Petaoctets | 400000 Tbit |
| 100 Petaoctets | 800000 Tbit |
| Reference | Petaoctets (Po) | Terabits (Tbit) |
|---|---|---|
| A plain text message (160 characters) | 1.6 × 10-13 Po | 0.00000000128 Tbit |
| A three-minute MP3 | 0.000000003 Po | 0.000024 Tbit |
| A smartphone photo | 0.000000004 Po | 0.000032 Tbit |
| A high-definition film | 0.000004 Po | 0.032 Tbit |
| A dual-layer Blu-ray disc | 0.00005 Po | 0.4 Tbit |
The petaoctet is a unit of digital information equal to a thousand teraoctets, or a million gigaoctets. Its symbol is Po. It is the unit of institutional storage: the scale at which data belongs to an organisation rather than to a person, and at which keeping it becomes a budget line rather than an afterthought.
A petaoctet is roughly the storage of a thousand large consumer hard drives, or the text of every book ever published several times over. In video terms it is about twenty thousand hours in ultra-high definition, or two and a half years of continuous viewing. The entire catalogue of a large streaming service, held once at each quality level, comes to a few petaoctets.
Science reached this scale first. The Large Hadron Collider at CERN records tens of petaoctets a year after its trigger systems have already discarded more than 99.99 per cent of what the detectors see, and the full archive runs to several hundred petaoctets. Astronomy, genomics and climate modelling all keep archives of comparable size, and the discipline of managing them became a research field of its own.
Commercially the petaoctet describes a single data centre's storage rather than a company's total. A large organisation holds tens or hundreds of petaoctets across many sites, and the largest cloud providers hold exaoctets. At this size the practical problems are not capacity but the electricity to keep the drives spinning, the cooling, and the certainty that a fraction of the hardware is failing at any moment.
That last point drives the design. In a petaoctet array, drive failures are not exceptional events but a continuous background rate, so the system is built to lose devices constantly and rebuild without interruption. Data is stored with erasure coding across many machines, and no single copy of anything is trusted.
Reading a petaoctet is itself a problem. Even at ten gigaoctets per second, a rate few systems sustain, a full pass takes more than a day. This is why analysis at this scale is designed to move the computation to the data rather than the data to the computation, an inversion that shaped the whole field of distributed processing.
One petaoctet equals 1,000 teraoctets, 1,000,000 gigaoctets, 8 petabits, or about 0.8882 pebioctets.
The terabit is a unit of digital information equal to one million million bits, a thousand gigabits. Its symbol is Tbit. It is the scale at which the internet's own infrastructure is measured — not the connection into a house, but the links between cities and across oceans.
A terabit is 125 gigaoctets. Put another way, one terabit is roughly the amount of data in a hundred and twenty-five hours of high-definition video, or the contents of a large laptop's disc. A single terabit-per-second link therefore moves the equivalent of that laptop every second, continuously.
Submarine cables are where these numbers live. A modern transoceanic cable carries several hundred terabits per second across a handful of fibre pairs, using wavelength division multiplexing to run dozens of separate light channels down the same glass strand at once. The cables laid across the Atlantic in the 2020s reach into the hundreds of terabits, where the first transatlantic telephone cable of 1956 carried thirty-six voice calls.
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 figures are among the most reliable public measurements of how much the internet is actually being used at a given moment.
Laboratory records go far higher. Research teams have pushed single optical fibres past a petabit per second by using multi-core fibre and hundreds of wavelengths simultaneously, though such experiments run over short distances under controlled conditions. The gap between what is demonstrated in a laboratory and what is deployed in the sea is usually about a decade.
For storage the terabit is used mainly in the semiconductor industry, where the density of a memory die is quoted in terabits per square centimetre or per package. Consumer products are labelled in octets instead — a terabit is 125 gigaoctets, so a chip described as 8 terabits appears on the shelf as a one-teraoctet drive.
One terabit equals 1,000,000,000,000 bits, 1,000 gigabits, 125 gigaoctets, or about 0.9095 tebibits.