Video-on-demand and other interactive television services are driving the development of video server technology. By their very nature these video servers are multiprocessor systems. This is especially true when the server is required to provide hundreds, thousands, or even hundreds of thousands of video streams. This paper reviews a number of the proposed video server architectures. These architectures differ in some key areas and this paper compares their advantages and disadvantages. Issues regarding their impact on software architecture, reliability, and cost are also discussed. Finally, a summary of areas for future work is presented.