Designing a Video on Demand Server
Designing a Video on Demand ServerDesigning a Video on Demand Server
INTRODUCTION
Video-on-demand (VoD) service will allow customers to request that certain movies or television shows be played on their television sets or computers immediately, giving individuals direct access to the materials stored in a video server. The goal of this project is to design a Video-on-Demand Server capable of performing to the following specifications:
� Capacity - 25 feature-length movies
� Serve 4 different movies simultaneously
� No loss of video/audio
� No "stutter" or skip
� 100% fault tolerance
As previously discussed in the cost estimate, the Video on Demand (VoD) Server will be based on a multi-processor x86 architecture. The VoD server with all elements described in the cost estimate (excluding RAID level 4 support) will be implemented on the Windows NT operating system running on a 500MHz dual-processor Pentium� III Xeon system with 512MB of memory. The configuration will consist of two Ethernet interfaces connected to an Ethernet switch on a T3 backbone, providing a peak network bandwidth of 30 Mbits/sec. Storage will consist of a set of four 18GB ULTRAWIDE SCSI-2 drives configured as a striped logical volume using standard Widows NT system tools. To further increase transfer speed, a 64MB hardware disk cache will also be used in the system. Arrays of optical drives will also be employed as secondary storage. The VoD Server will be linked to an array of Uninteruptable Power Supplies (UPS) capable of supplying 10 minutes of backup power.
Similar servers were tested in this configuration with multiple client access and was able to saturate the network with 150 clients playing MPEG1 and 2 streams. The effective network usage was 25 Mbits/sec. However, the network is saturated at this level due to the overhead associated with the TCP protocol. I expect CPU utilization vs. number of clients to be nearly linear as the number of clients increase.
In the following pages, I will discuss the qualities of an effective video server. Furthermore, I will also discuss the qualities of the video server which I have designed for this project.
HARDWARE
ARCHITECTURE
Video servers are basically large repositories for data and information which are provided on demand to clients. The VoD server architecture can be defined by the way the data is stored within the video server. Data can be stored locally within a server or can be distributed across a large number of servers. Thus, two distinct methodologies exist for video server configuration:
Autonomous Servers: Video servers of this type can be viewed as stand-alone entities since they store encoded streams locally to themselves and. thus, do not require the cooperation of other servers to serve a VoD client. The actual physical implementation and the logical implementation of the video server are relatively the same. The server usually consists of a CPU, a storage medium (which can consist of a standard storage...
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