A Model and Prototype of a Resource-Efficient Storage Server for High-Bitrate Video-on-Demand

This paper presents a mathematical model and a prototype of a resource-efficient storage server for high-bitrate video-on-demand (VoD) applications. Rapid exponential growth of disk capacity enables the storage of high-bitrate VoD streams; however, a server system must be carefully designed to allow those streams to be retrieved from disk and delivered to the network efficiently. Additionally, a cost-effective server should be implemented using only commodity components, such as standard PCs, SATA disks and controllers, and Gigabit Ethernet links. This paper presents a model: detailed enough to account for the rate-based nature of streaming video, the buffering time allowed by the application, and average-case disk hardware characteristics while remaining simple enough to use for algorithm and system design. This paper then describes a prototype storage server designed to serve large video files at the specified bitrates and finds its performance to agree closely with the model (with an average discrepancy of 11% for high-bitrate streams). The system uses up to 8 SATA-300 disks and can simultaneously serve 290 distinct DVD-quality (6 Mbps) streams or 74 distinct HDTV-quality (25 Mbps) streams from disk, achieving an aggregate network throughput of 1.85 Gbps.