(Linear Tape Open) A family of open magnetic tape standards developed by HP, IBM and Quantum (formerly the Certance subsidiary of Seagate) that are licensed to third-party vendors. LTO cartridges contain a memory that stores historical usage data. Although LTO was introduced with a native capacity of only 100GB, multi-terabyte tapes followed. Starting with LTO-3, write once-read many (WORM) support was added, and LTO-4 built in hardware encryption (see table below). See WORM. LTO Is Ultrium In 1998, two formats were announced: a single-hub Ultrium, like DLT cartridges, and a dual-hub Accelis, similar to Magstar MP. Sharing read/write head, track layout and other features, the single-hub Ultrium was accepted, while Accelis never took off. For information, visit www.lto-technology.com. See DLT and Magstar MP.