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Big data is an emerging phenomenon characterized by the three Vs: volume, velocity, and variety. The volume of data has increased from terabytes to petabytes and is encroaching on exabytes. Some pundits are suggesting that zettabytes (1021) are reachable within the next several years. Velocity is concerned with not only how fast we accumulate data, but also how fast some of the data that we already have is changing. Some systems accumulate data at the rate of multiple petabytes per year, some systems have stored data that changes at the rate of terabytes per year. Changing data usually lags accumulating data by several orders of magnitude. Data accumulating at a multiple petabyte rate requires terabits to petabits of transport capacity. Finally, the variety and modality of data is continually evolving, it may be both structured and unstructured.