Recent progress in network technologies has made it possible to integrate digital video and audio into distributed computing environments. Among the various distributed multimedia applications, video-on-demand (VOD) services are the most typical application area. However, interest in large-scale VOD systems is gradually transferring to small and low-cost VOD systems because of the excess investment required in the transmission media. When we make a small-scale VOD system, one of the most important factors is the efficient resource management of the VOD server in order to achieve cost-effectiveness. Thus, multimedia has generated widespread interest in real-time and high-performance I/O support within general-purpose operating systems. This paper presents the performance of a small-scale, UNIX-based VOD server equipped with a real-time scheduler and a continuous media file system (CMFS). The real-time scheduler is based on the theory of non-preemptive real-time systems to test schedulability within polynomial time. To reduce interference of the interrupt processing for the real-time processes, the processes are classified into two groups in order of importance. The CMFS has been designed and implemented to acquire the performance of the raw disk. According to the analysis of the measured data, UNIX can efficiently transfer video data from disk to network and it can also guarantee most deadlines.
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