| Pebioctets (Pio) | Zettabits (Zbit) |
|---|---|
| 1 Pebioctet | 0.00000900719925474 Zbit |
| 2 Pebioctets | 0.0000180143985095 Zbit |
| 3 Pebioctets | 0.0000270215977642 Zbit |
| 4 Pebioctets | 0.000036028797019 Zbit |
| 5 Pebioctets | 0.0000450359962737 Zbit |
| 10 Pebioctets | 0.0000900719925474 Zbit |
| 20 Pebioctets | 0.000180143985095 Zbit |
| 25 Pebioctets | 0.000225179981369 Zbit |
| 50 Pebioctets | 0.000450359962737 Zbit |
| 100 Pebioctets | 0.000900719925474 Zbit |
| Reference | Pebioctets (Pio) | Zettabits (Zbit) |
|---|---|---|
| A plain text message (160 characters) | 1.42109 × 10-13 Pio | 1.28 × 10-18 Zbit |
| A three-minute MP3 | 0.00000000266454 Pio | 2.4 × 10-14 Zbit |
| A smartphone photo | 0.00000000355271 Pio | 3.2 × 10-14 Zbit |
| A high-definition film | 0.00000355271 Pio | 3.2 × 10-11 Zbit |
| A dual-layer Blu-ray disc | 0.0000444089 Pio | 4 × 10-10 Zbit |
The pebioctet is a unit of digital information equal to 1,125,899,906,842,624 octets, which is 1,024 tebioctets. Its symbol is Pio. It is the binary counterpart of the petaoctet, and the two now differ by 12.6 per cent.
This is the unit in which filesystem limits are written. Several widely deployed filesystems have maximum file or volume sizes that are exact powers of two, and those limits fall in this range: sixteen tebioctets for one, a pebioctet for another, eight pebioctets for a third. The numbers are not choices made by anyone; they follow from how many bits the filesystem uses to number its blocks.
Large scientific and commercial storage systems are also sized here. A research computing centre may run a filesystem of several pebioctets across thousands of drives, and the tools that manage it report in pebioctets because the underlying allocation is binary throughout. Converting those figures to decimal units for a report introduces an error of an eighth for no benefit.
A pebioctet is roughly a thousand large consumer hard drives, or the complete video output of a broadcaster over many years. It is also close to the size of the largest single scientific archives, though those are typically stated in petaoctets by press offices and in pebioctets by the engineers who run them, which produces two different numbers for the same building.
Distinguishing the two is not pedantry at this level. A twelve per cent difference on a purchase of many pebioctets is a large sum of money, and a capacity plan built on the wrong unit will be wrong by more than the margin most plans allow. This is precisely the situation the IEC prefixes were introduced to prevent.
The symbol Pio is used in filesystem documentation, in storage system manuals and in standards. Where a source writes PB without saying which it means, the difference is an eighth, and the honest thing for a reader to do is treat the figure as approximate rather than assume one convention or the other.
One pebioctet equals 1,024 tebioctets, 1,125,899,906,842,624 octets, 8 pebibits, or about 1.126 petaoctets.
The zettabit is a unit of digital information equal to a thousand exabits, or a sextillion bits — a one followed by twenty-one zeros. Its symbol is Zbit. It is the largest unit in which real, measured quantities of data are still routinely reported, and it entered common use only in the last fifteen years.
A zettabit is 125 exaoctets. The phrase that made the prefix familiar was the zettabyte era, coined for the moment around 2016 when annual global internet traffic first exceeded one zettaoctet. That threshold arrived a little over a decade after annual traffic first passed one exaoctet, which gives a fair sense of the growth rate involved.
Estimates of the total quantity of data in existence are given in zettaoctets. The global datasphere — everything stored on every server, disc, phone and memory card, plus everything created and immediately discarded — is put at somewhere above a hundred zettaoctets, which is more than eight hundred zettabits. Nobody counts this directly; the figures come from manufacturing statistics and modelling.
Almost all of that is machine-generated and never read by anyone. Surveillance video that is recorded and overwritten, sensor telemetry, logs, backups and the many copies that redundancy demands account for the overwhelming majority. The portion that a human being has ever looked at is a tiny fraction of the total, and shrinking as a share every year.
The prefix zetta was adopted in 1991, along with yotta, at a conference that also had to consider what letters remained available. Z and Y were chosen partly because they were unused, and the pattern of naming from the Greek and Latin numerals had by then become loose. The 2022 additions of ronna and quetta continued the ladder upward for the same reason.
For perspective, a zettabit of information written as text in a single line of characters would stretch far beyond the solar system. The unit does not describe anything a person can hold or handle; it describes a civilisation's accumulated output, and it is useful precisely because that quantity now needs a name.
One zettabit equals 1,000 exabits, 125 exaoctets, or about 0.8470 zebibits.