| Petaoctets (Po) | Zebibits (Zibit) |
|---|---|
| 1 Petaoctet | 0.00000677626357803 Zibit |
| 2 Petaoctets | 0.0000135525271561 Zibit |
| 3 Petaoctets | 0.0000203287907341 Zibit |
| 4 Petaoctets | 0.0000271050543121 Zibit |
| 5 Petaoctets | 0.0000338813178902 Zibit |
| 10 Petaoctets | 0.0000677626357803 Zibit |
| 20 Petaoctets | 0.000135525271561 Zibit |
| 25 Petaoctets | 0.000169406589451 Zibit |
| 50 Petaoctets | 0.000338813178902 Zibit |
| 100 Petaoctets | 0.000677626357803 Zibit |
| Reference | Petaoctets (Po) | Zebibits (Zibit) |
|---|---|---|
| A plain text message (160 characters) | 1.6 × 10-13 Po | 1.0842 × 10-18 Zibit |
| A three-minute MP3 | 0.000000003 Po | 2.03288 × 10-14 Zibit |
| A smartphone photo | 0.000000004 Po | 2.71051 × 10-14 Zibit |
| A high-definition film | 0.000004 Po | 2.71051 × 10-11 Zibit |
| A dual-layer Blu-ray disc | 0.00005 Po | 3.38813 × 10-10 Zibit |
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 zebibit is a unit of digital information equal to two to the seventieth power bits, which is 1,024 exbibits. Its symbol is Zibit. It is the binary counterpart of the zettabit, and the two now differ by 18.1 per cent — nearly a fifth.
That divergence is the reason the binary prefixes were needed at all. At the kibibit the two conventions differed by 2.4 per cent, a rounding error. Here the difference is large enough that a document using the wrong one is simply reporting a different quantity, and no amount of context can repair the ambiguity after the fact.
A zebibit is 147,573,952,589,676,412,928 octets, or 128 exbioctets. Nothing of this size exists. The total data held by humanity is somewhere in the low hundreds of zettaoctets, which is under a zebioctet, so the world's entire information stock does not yet reach one unit at this step of the binary ladder.
The unit exists because the IEC series was defined completely rather than as far as anyone then needed. That is the same principle the metric system follows: every prefix applies to every unit, whether or not the combination has yet been used. A system with holes in it requires a table of exceptions, and a system without holes requires only the rule.
Where the zebibit could genuinely appear is in address space arithmetic. Two to the seventieth is not a natural pointer width, but multiples and fractions of powers of two run through every discussion of addressing, and a scheme that reserved seventy bits for something would naturally be described in these terms. Such schemes are proposed occasionally and none has yet been needed.
Reading the symbol is the practical skill. Zibit is binary, Zbit is decimal, and at eighteen per cent apart the two are not interchangeable in any document where the number matters. Where a source writes ZB with no explanation, there is no way to know which was meant, and the honest response is to treat the figure as uncertain to a fifth.
One zebibit equals 1,024 exbibits, 147,573,952,589,676,412,928 octets, or about 1.181 zettabits.