Stratus VOS

Stratus VOS (Virtual Operating System, now renamed as OpenVOS) is a proprietary operating system running on Stratus Technologiesfault-tolerant computer systems. VOS is available on Stratus's ftServer and Continuum platforms. VOS customers use it to support high-volume transaction processing applications which require continuous availability. VOS is notable for being one of the few operating systems which run on fully lockstepped hardware.

During the 1980s, an IBM-branded version of Stratus VOS existed and was called the System/88 Operating System.