 Master copies of digital films from movie studios are stored on Amazon S3, and each film is encoded into over 50 different versions based on video resolution and audio quality using machines on the cloud.In total, Netflix has over 1 petabyte of data stored on Amazon, and the data is sent to content delivery networks (including Akamai Technologies, Limelight Networks and Level 3 Communications) that feed the content to local ISPs.Netflix uses a number of pieces of open-source software in its backend, including Java, MySQL, Gluster, Apache Tomcat, Hive, Chukwa, Cassandra and Hadoop.