Design and Analysis of a Fault-Tolerant Mechanism for a Server-Less Video-On-Demand System

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 service 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.