Abstract: The Dawning super\|server is a typical cluster system, for which a COSMOS file system has been developed. Mainly presented in this paper are the design, implementation, and evaluation of the prototype COSMOS file system. Here highlit are some key technologies including dual\|granularity cooperative caching, distributed meta\|data management, and network disk stripping. The performance of the prototype file system is also evaluated using the standard I/O benchmarks. The initial performance measurements show that our approach is a promising one in providing scalable single\|image file system.