Hitachi announced the HITAC FT6100 in October 1991, which was designed as a fault-tolerant server. Due to its hardware redundancy, the server could continue processing on one system if a fault developed in another system. Processors in particular could be easily added or replaced since the triply-redundant functional modules were implemented on a single processor board. The machine’s multiprocessing performance could be boosted by adding more processor boards.
Hitachi also developed the UNIX-based HI-UX/F operating system with enhanced real-time functionality, which made it possible to program with standard open-source interfaces.
This combination of features resulted in a fault-tolerant server that supported uninterrupted computer system operation and permitted system expansions and maintenance and software updating without stopping operations.