Castor: CERN Advanced STORage Manager

CASTOR is a hierarchical storage management system developed at CERN that combines disk and tape storage to archive massive volumes of physics data, offering access through command-line tools and APIs with protocols like XROOT and GridFTP. The system uses a component-based architecture with a central database to manage disk pools (via Stager), file metadata (via Name Server), and tape operations, with tape storage providing cost-effective long-term archiving despite slower access times. As of June 2020, CASTOR has been gradually replaced by CTA (CERN Tape Archive) as the successor system.