Petabit to Petabyte

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 petabyte (PB) = 1,000 terabytes (TB) in the SI decimal system. In the binary IEC system, 1 pebibyte (PiB) = 1,024 tebibytes (TiB) = 1,125,899,906,842,624 bytes. The distinction matters for enterprise storage procurement: a petabyte of raw disk capacity appears as about 909 TiB in an OS reporting binary units.

Petabyte-scale storage is common at: social media platforms (Facebook/Meta stores over 100 PB of photos alone), streaming services (Netflix's content library is estimated at 100+ PB), government agencies (US NSA, CERN particle physics data), genomic research institutions, and large financial exchanges storing tick-level trading data. Major cloud providers (AWS, Azure, GCP) collectively store zettabytes.

In 2024, cloud storage costs roughly $20–25 per TB per month (S3 standard tier), making 1 PB approximately $20,000–$25,000/month. Raw enterprise disk hardware for 1 PB runs about $20,000–$50,000 upfront (at $20–50 per TB for high-density drives), plus ongoing power, cooling, and management overhead. Tape-based archival storage is considerably cheaper at $2–5 per TB.

YouTube users upload approximately 500 hours of video per minute, or 720,000 hours per day. At an average compressed size of 1–2 GB per hour of HD video, that equates to roughly 720–1,440 TB (0.7–1.4 PB) of new video data per day — before YouTube re-encodes into multiple formats and quality levels, which multiplies storage requirements several-fold.

The SI prefix hierarchy above petabyte: exabyte (EB, 10¹⁸ bytes), zettabyte (ZB, 10²¹ bytes), yottabyte (YB, 10²⁴ bytes), ronnabyte (RB, 10²⁷ bytes), and quettabyte (QB, 10³⁰ bytes) — the last two added by the BIPM in 2022. Current global data storage is estimated in the hundreds of exabytes; no single organisation approaches yottabyte scale.