Big data describes large sets of varied data – structured, unstructured, and semi-structured—constantly generated at high speed and volume. Terabytes or petabytes are commonly used measurements for big data. One million gigabytes make up one petabyte. To put this into perspective, consider that one HD movie contains about 4 gigabytes of data. One petabyte is equivalent to 250,000 movies. Big data is measured in hundreds, thousands, and millions of petabytes.