Buffer management and dimensioning for a pull-based parallel video server

Recently, there has been a trend toward designing video-on-demand systems using parallel-server architectures. By exploiting server-level parallelism, researchers can break through the performance limit of a single server, while keeping the system cost low by leveraging on commodity hardware platforms. A number of studies have demonstrated the feasibility of building parallel video servers around the client-pull architecture and one can even incorporate data redundancy into the system to sustain server-level failures. However, due to randomness of request arrivals and server processing time, dimensioning the server resource requirement is often difficult. This paper tackles the problem of buffer management and dimensioning for such a pull-based parallel video server. Using a generic buffer-pool model with worst-case analysis, upper bounds on the server buffer requirement are derived for a parallel-server design with multiple disks per server. The obtained bounds are independent of placement policy, video bit-rate, disk-scheduling discipline, and even number of servers in the system, making it applicable to a wide range of server designs. The analytical results also proved that the scalability of this pull-based server design will not be limited by the server buffer requirement.