Peta- is a prefix in the metric system denoting 1015 or 1,000,000,000,000,000 (1 quadrillion). For example:
The Blue Waters project will deliver a supercomputer capable of sustained performance of 1 petaflop on a range of real-world science and engineering applications. It is expected to be one of the most powerful supercomputers in the world. Think of that power.
A human doing a single mathematical calcluation per second would take about thirty-two years to complete 1 billion calculations. America was celebrating its bicentennial, and the first commercially developed supercomputer—the Cray-1—was being released.
But that's nothing compared to 1 trillion calculations. At one calculation per second, you'd be starting 31 thousand years ago, when cavemen were creating the earliest cave paintings.
Now move to 1 quadrillion calculations. You're beginning 31 million years ago, during the Cenozoic era. The Alps were beginning to rise in Europe, and ancestors to modern horses, dogs, and apes were coming on the scene.
1 petabyte (PB) of disk storage is equivalent to:
60 years of data collection from the Sloan Digital Sky Survey
126 Libraries of Congress
more than 212,000 DVDs
40,000 single-layer Sony
more than 4 trillion 200-page books
250 billion mp3 music files