| Gigaoctets (Go) | Zebioctets (Zio) |
|---|---|
| 1 Gigaoctet | 8.47032947254 × 10-13 Zio |
| 2 Gigaoctets | 1.69406589451 × 10-12 Zio |
| 3 Gigaoctets | 2.54109884176 × 10-12 Zio |
| 4 Gigaoctets | 3.38813178902 × 10-12 Zio |
| 5 Gigaoctets | 4.23516473627 × 10-12 Zio |
| 10 Gigaoctets | 8.47032947254 × 10-12 Zio |
| 20 Gigaoctets | 1.69406589451 × 10-11 Zio |
| 25 Gigaoctets | 2.11758236814 × 10-11 Zio |
| 50 Gigaoctets | 4.23516473627 × 10-11 Zio |
| 100 Gigaoctets | 8.47032947254 × 10-11 Zio |
| Reference | Gigaoctets (Go) | Zebioctets (Zio) |
|---|---|---|
| A plain text message (160 characters) | 0.00000016 Go | 1.35525 × 10-19 Zio |
| A three-minute MP3 | 0.003 Go | 2.5411 × 10-15 Zio |
| A smartphone photo | 0.004 Go | 3.38813 × 10-15 Zio |
| A high-definition film | 4 Go | 3.38813 × 10-12 Zio |
| A dual-layer Blu-ray disc | 50 Go | 4.23516 × 10-11 Zio |
The gigaoctet is a unit of digital information equal to one thousand million octets, or eight gigabits. Its symbol is Go. It is the unit in which most things people actually buy are sized: the memory in a computer, the storage in a phone, the monthly allowance on a mobile contract.
The reference points are familiar. A DVD holds 4.7 gigaoctets and a dual-layer disc 8.5. A Blu-ray holds 25 or 50. A feature film in high definition is 4 to 15 gigaoctets depending on compression, and in ultra-high definition 40 or more. A phone with 128 gigaoctets of storage holds roughly thirty thousand photographs, or a few hundred hours of music.
Memory sizes now sit in this range and are stated in gibioctets even when written as gigaoctets. A module labelled 8 GB holds 8 gibioctets, which is 8.59 gigaoctets, because memory addressing is binary and always has been. The same is true of processor caches and of the page tables that map memory, so anything on the memory side of a computer is binary while anything on the storage side is decimal.
That split is the source of the most familiar consumer complaint about units. A hard drive sold as one teraoctet holds a million million octets, which the operating system divides by 1,024 three times and reports as 931 gigaoctets. Nothing has been lost; the drive holds exactly what the box says, but the two are counting in different bases. Lawsuits over this were settled in the manufacturers' favour, since the decimal usage matches the metric system.
Mobile data allowances made the gigaoctet a household figure. A few gigaoctets a month was generous around 2012 and is now minimal, because video dominates: an hour of standard-definition streaming is about 0.7 gigaoctets, an hour in high definition around 3, and an hour in ultra-high definition 7 or more.
For scale in text, a gigaoctet holds around a thousand full-length books as plain text, or the complete works of most authors many times over. Digital storage stopped being a constraint on text decades ago, and every capacity discussion since has really been about images, sound and video.
One gigaoctet equals 1,000,000,000 octets, 1,000 megaoctets, 8 gigabits, or about 0.9313 gibioctets.
The zebioctet is a unit of digital information equal to two to the seventieth power octets, which is 1,024 exbioctets. Its symbol is Zio. It is the binary counterpart of the zettaoctet, and the two differ by 18.1 per cent.
Nothing of this size exists. The total quantity of data held by humanity, counting every copy and every backup, is estimated in the low hundreds of zettaoctets, and a zebioctet is 1.18 zettaoctets, so the world holds a few hundred of these units in total. It is the first binary unit for which the world's entire stock is a small multiple rather than a large one.
The unit is defined for completeness rather than for use, which is a deliberate feature of both the metric and the IEC systems. Every prefix applies to every unit without exception, so a reader who has never seen Zio can decode it from the prefix alone. A system that ran out of names at some arbitrary point would force each future user to invent an extension, and rival extensions are how ambiguity is born.
There is one place where the unit would arise naturally. Storage addressing beyond 64 bits has been designed but not needed: the ZFS filesystem uses 128-bit block pointers, giving it a theoretical capacity far beyond any binary prefix that has a name. Where such a scheme states intermediate limits, those limits fall in this range and are properly written in zebioctets.
The 18.1 per cent gap between zebioctet and zettaoctet is worth holding in mind when reading forecasts. Predictions of global data growth are published in zettaoctets, and any that were computed in binary and reported in decimal are nearly a fifth off. Given that such forecasts are already rough, that error is not the largest source of uncertainty, but it is an avoidable one.
The symbol Zio, like all the IEC symbols, is a capital letter followed by lowercase i and then the unit. It is the presence of that i, rather than any statement in the text, that tells a reader unambiguously which quantity is meant, and a document that omits it has not said what it appears to have said.
One zebioctet equals 1,024 exbioctets, 1,180,591,620,717,411,303,424 octets, 8 zebibits, or about 1.181 zettaoctets.