Hadoop, along with its related architectures, is open-source technology that enables the processing of vast amounts of data. While the technology is relatively new, the emerging industry surrounding it could be big: IDC estimates the markets for dynamic data management, content analytics software, and advanced analytics software will reach $22.1 billion by 2020.Also enticing for investors: There are currently only four players that sell these specific big data tools, two "pure plays" -- Cloudera (NYSE: CLDR) and Hortonworks (NASDAQ: HDP) -- private company MapR, and Amazon's Elastic MapReduce.