The ESO Data Transfer System

As of July 2008 all data produced at the ESO Paranal Observatory are transferred automatically to the main archive in Garching via the internet, reducing the "time to archive" from several days to a few minutes or hours. The almost immediate availability of data in Garching will significantly speed up the quality-control feedback loop to Paranal and will result in a better service provided to the ESO community. This paper describes some of the technical challenges of transferring large volumes of data over a high-latency network with "just enough" bandwidth, and the solutions we adopted to optimize the bandwidth usage and to provide a highly reliable, flexible, priority-based transfer.