Performance Study on Video Placement and Load Balancing of Distributed Video-On-Demand Systems

Abstract

Distributed VOD server is a solution to the problem of the capacity limit posed by single server system. There needs to be an algorithm for the head-end to use to evaluate the current status of traffic loading in the whole VOD system, so that it can decide whether a new user request should be served locally, forwarded to a remote server, or simply be rejected. The computation is further complicated by the fact that server capacities and communication costs between different servers may be variab1e. In this paper, we first define a mathematical model used to analyze the performance of our VOD systems. We then present an algorithm to compute the number of copies each film should be duplicated, as well as where to p1ace them in order to gain maximum revenue. Numerical results show that our algorithm offers improvement over Chen's algorithm [7]. We also present a method to evaluate whether a new user request should be served locally, or forwarded to a remote server, or simply be rejected. It can be seen under the prerequisite of maximal revenue that while a local video server is too busy to serve a local request, it is a good idea to send it to a remote video server which has extra capacity to process it.