The next largest unit of data storage after the terabyte is the petabyte which is abbreviated PB. Just as a terabyte is approximately equal to 1000 gigabytes, a petabyte is approximately equal to 1000 terabytes. A petabyte contains 1,000,000,000,000,000 bytes which is read as one quadrillion bytes.
A petabyte can store a very large amount of data. For example, one PB of storage can hold five years worth of data from NASA's Earth Observing System, which is a series of satellites and scientific instruments that orbit the Earth and make global observations. Two petabytes can contain the data from every academic research library in the United States.
The next unit after the petabyte is the exabyte which is abbreviated EB. An exabyte is equal to 1000 petabytes and contains 1,000,000,000,000,000,000, or one quintillion bytes. It is hypothesized that five exabytes could hold all the words ever spoken by humans throughout history.
After the exabyte comes the zettabyte, which is equal to 1000 exabytes and is abbreviated ZB. A zettabyte contains one sextillion bytes which is written as a one with 21 zeros behind it.
Finally, the largest unit of digital storage is the yottabyte, abbreviated YB. A yottabyte is 1000 zettabytes and contains one septillion bytes which is a one with 24 zeros.