Poster on A Distributed RAID VOD System

pseudo-client program] In this poster, we present an implementation of a VOD (Video on Demand) system that addresses the problem of increasing video stream supplying capabilities. To get fundamental data of video stream transferring characteristics on Ethernet, we first made an experiment in which it became clear that bottlenecks of CPU of a video server was the most serious. To solve this problem we implemented a distributed RAID4 (Redundant Arrays of Inexpensive Disks) method video server. “Distributed RAID” means extending the RAID method usually applied to disks to the servers, so as to achieve improvements in performance and reliability.(Fig.l) The great advantage of this architecture is that the linear performance improvement can be achieved by adding inexpensive servers of a difision model. Swift is an early implementation of distributed RAID at California University[l]. As this system was not an video server system, only usual data (not video data) transfer tests were reported, and the performance improvement was not proportional to the number of servers. On the contrary, we used video data and tested the system by checking frame drop rates as well as observing picture quality to check the applicability for video servers. An scalable performance improvement proportional to the number of servers was measured. It was also true in degradation mode in which one of the servers is dropped by failure. Moreover, our experiment is nearer to practical systems in the point that the data transfer rate in the test(41.2Mbps) is much higher than Swift case(around 8Mbps). Finally, we also made a dynamic one server drop test successfully, with no infulence to moving pictures. [Video data] For testing more than 6 clients, we made and used a pseudo-client program, which were loaded on each client and behaved as if there were more than one client. Servers Pen&m SOMIIz, Memory 32MB, 1GB Disks X 3 Windows NT erver Vcrsio 3.5 server 0 server 1 server L