| Zebibits (Zibit) | Pebioctets (Pio) |
|---|---|
| 1 Zebibit | 131072 Pio |
| 2 Zebibits | 262144 Pio |
| 3 Zebibits | 393216 Pio |
| 4 Zebibits | 524288 Pio |
| 5 Zebibits | 655360 Pio |
| 10 Zebibits | 1310720 Pio |
| 20 Zebibits | 2621440 Pio |
| 25 Zebibits | 3276800 Pio |
| 50 Zebibits | 6553600 Pio |
| 100 Zebibits | 13107200 Pio |
| Reference | Zebibits (Zibit) | Pebioctets (Pio) |
|---|---|---|
| A plain text message (160 characters) | 1.0842 × 10-18 Zibit | 1.42109 × 10-13 Pio |
| A three-minute MP3 | 2.03288 × 10-14 Zibit | 0.00000000266454 Pio |
| A smartphone photo | 2.71051 × 10-14 Zibit | 0.00000000355271 Pio |
| A high-definition film | 2.71051 × 10-11 Zibit | 0.00000355271 Pio |
| A dual-layer Blu-ray disc | 3.38813 × 10-10 Zibit | 0.0000444089 Pio |
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.
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.