| Gigaoctets (Go) | Pebibits (Pibit) |
|---|---|
| 1 Gigaoctet | 0.0000071054273576 Pibit |
| 2 Gigaoctets | 0.0000142108547152 Pibit |
| 3 Gigaoctets | 0.0000213162820728 Pibit |
| 4 Gigaoctets | 0.0000284217094304 Pibit |
| 5 Gigaoctets | 0.000035527136788 Pibit |
| 10 Gigaoctets | 0.000071054273576 Pibit |
| 20 Gigaoctets | 0.000142108547152 Pibit |
| 25 Gigaoctets | 0.00017763568394 Pibit |
| 50 Gigaoctets | 0.00035527136788 Pibit |
| 100 Gigaoctets | 0.00071054273576 Pibit |
| Reference | Gigaoctets (Go) | Pebibits (Pibit) |
|---|---|---|
| A plain text message (160 characters) | 0.00000016 Go | 1.13687 × 10-12 Pibit |
| A three-minute MP3 | 0.003 Go | 0.0000000213163 Pibit |
| A smartphone photo | 0.004 Go | 0.0000000284217 Pibit |
| A high-definition film | 4 Go | 0.0000284217 Pibit |
| A dual-layer Blu-ray disc | 50 Go | 0.000355271 Pibit |
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 pebibit is a unit of digital information equal to 1,125,899,906,842,624 bits, which is 1,024 tebibits or two to the fiftieth power. Its symbol is Pibit. It is the binary counterpart of the petabit, and the gap between them has widened to 12.6 per cent.
That widening is worth watching, because it is the whole argument for the IEC prefixes in one number. Each step up the ladder multiplies the discrepancy by 1.024, so what began as a harmless 2.4 per cent at the kibibit is an eighth of the quantity here and a fifth at the yobibit. A convention that was reasonable for small numbers becomes indefensible for large ones.
A pebibit is 140,737,488,355,328 octets, or 128 tebioctets. Storage of this size exists in supercomputer memory systems, in the fastest scientific data buffers and in the aggregate memory of very large clusters. The largest machines on the list of the world's fastest computers have main memory measured in pebioctets, and the ability to hold an entire simulation in memory rather than on disc is what makes certain calculations feasible at all.
Because these systems are addressed in binary, the binary unit is the correct one and the decimal figure would be an approximation. A cluster with a pebibit of memory does not have a petabit; it has 12.6 per cent more, and a scheduler that allocated on the decimal figure would leave that much unused.
The unit also appears in filesystem limits. Several widely used filesystems have maximum volume or file sizes expressed as exact powers of two, and where those limits fall in this range they are naturally written in pebibytes or pebioctets. Documentation that converts them to decimal units loses the property that made them memorable.
In everyday computing the pebibit is never encountered. It belongs to specifications, to system architecture and to the design of the largest machines, and a converter needs it for exactly those documents. Anywhere the underlying quantity is a power of two, this is the unit that says so without rounding.
One pebibit equals 1,024 tebibits, 140,737,488,355,328 octets, or about 1.126 petabits.