Petabit to Terabyte

One petabit = 10¹⁵ bits = 125 terabytes. To put it in perspective: the entire text content of all English Wikipedia articles is roughly 4 GB — so a petabit could hold about 31,000 copies of it. A petabit per second link could transfer all of Wikipedia's text content in about 32 microseconds.

As of 2024, no single commercial link carries 1 Pbps, but laboratory experiments have demonstrated fiber optic transmission exceeding 1 Pbps using dense wavelength-division multiplexing on a single fiber strand. Commercial submarine cables aggregate hundreds of terabits per second across many fibers and wavelengths, collectively reaching petabit-scale capacity per cable system.

A petabit (Pb) = 10¹⁵ bits. A petabyte (PB) = 10¹⁵ bytes = 8 petabits. Storage systems (data centers, archival systems) use petabytes for capacity; aggregate network throughput uses petabits per second. An exabyte-scale data center stores 1,000 petabytes; its internal network may carry multiple petabits per second of traffic.

Qubits and classical bits solve fundamentally different problems — qubits will not simply replace petabit-scale classical storage or networking. A quantum computer with 1,000 logical qubits can explore 2¹⁰⁰⁰ states simultaneously, but measuring those qubits collapses them to classical bits. Quantum networks will likely handle key distribution and entanglement sharing at kilobit-to-megabit rates, while classical infrastructure continues to move petabits of bulk data. The two technologies are complementary, not substitutional.

Submarine fiber optic cables are built by a handful of companies (SubCom, NEC, Alcatel Submarine Networks) and typically cost $200–500 million per system. A modern cable contains 12–24 fiber pairs, each carrying hundreds of wavelengths via dense wavelength-division multiplexing, reaching 400+ Tbps aggregate capacity per cable. Cables are designed to last 25 years on the ocean floor. When faults occur, specialised cable repair ships (fewer than 60 exist worldwide) locate breaks using optical time-domain reflectometry and splice repairs at sea — a process that can take days to weeks depending on depth and weather.

1 terabyte (TB) = 1,000 gigabytes (GB) in the SI decimal system. In the binary IEC system, 1 tebibyte (TiB) = 1,024 gibibytes (GiB). Consumer hard drives and SSDs are labelled in decimal TB; operating systems may display available space in either GB or GiB depending on the OS and version, leading to a discrepancy of up to ~7% between the label and the OS display.

A 1 TB SSD holds approximately: 200,000 JPEG photos (at 5 MB each), 250 HD movies (at 4 GB each), 200+ modern AAA games (at 50 GB average), or enough for about 100 hours of 4K video footage from a modern camera. In practice, the OS and drive firmware overhead reduce usable capacity to roughly 900–930 GB as reported by the operating system.

A terabyte (TB) = 10¹² bytes = 1,000,000,000,000 bytes. A tebibyte (TiB) = 2⁴⁰ bytes = 1,099,511,627,776 bytes. The TiB is about 9.95% larger. This gap is why a 1 TB hard drive appears as 931 GiB (≈ 0.909 TiB) in Windows. The IEC formally defined TiB in 1998 to eliminate this naming ambiguity.

Timeline depends heavily on use case: continuous 4K video recording fills 1 TB in about 2–3 hours (at 1 GB/min). Typical laptop use (documents, photos, apps) might take 3–5 years to fill 1 TB. A game library of 20 modern AAA titles uses 500 GB–1 TB. Home security camera systems recording 24/7 at 1080p use about 1 TB every 10–15 days per camera.

For most individuals, 1 TB of cloud storage is generous: it holds 200,000+ photos, years of documents, and even video libraries. Google One offers 2 TB for €9.99/month; iCloud offers 2 TB for £6.99/month. Power users — especially photographers and videographers — may need 2–5 TB. Family sharing plans can make 2 TB cost-effective across multiple users.