Design and analysis of a fault-tolerant mechanism for a server-less video-on-demand system
J.Y.B. Lee, R.W.T. Leung · 2003
Video-on-demand (VoD) systems have traditionally been built on the client-server architecture, where a video server stores, retrieves, and transmits video data to video clients for playback This paper investigates a radically different approach to building VoD systems, one where the server, and hence the primary bottleneck, is completely eliminated. This server-less architecture comprises homogeneous hosts, called nodes, which serve both as client and as mini-server. Video data are distributed over all nodes and these nodes cooperatively stream video data to one another for playback. However, unlike traditional video server that runs on high-end server hardware in a carefully controlled and protected data centre, a node in a server less system is likely to be far more unreliable. Therefore it is essential that sufficient data and capacity redundancies are incorporated to maintain an acceptable set-vice reliability. This paper presents and analyzes a fault tolerant mechanism based on inter-node striping and erasure correction codes to tackle this challenge. By formulating the system's reliability as a Markov chain model, we obtain insights into the feasible operating region of the system, such as the amount of redundancy required and the node-level reliability that can be tolerated. Numerical results show that a server-less VoD system of 200 nodes can achieve reliability surpassing that of dedicated video server using a redundancy overhead of only 21.2% even though individual nodes are highly unreliable.