Hiroaki Sakamoto

Storage hierarchy for video-on-demand systems

In this paper, we evaluate the performance of our trial hierarchical storage server by using simulation. Our system is composed of magnetic disk drives and an optical mass storage system (MSS). This is based on three key techniques: (1) multiple readout control using the time slot synchronous method, (2) quick access control of the MSS by using magnetic disk drives, (3) a storage hierarchy method for video programs that has three configurations. To verify the effectiveness of our storage hierarchy, we construct a queuing network simulation model of the system based on experimentally measured values, and analyze the average waiting time for each of the three configurations of video programs. Selecting the appropriate video program configuration shortens the average waiting time to half of previous times, with a quick access of less than 1 second, and with 8 simultaneous readouts. Storage costs are reduced to about half that of magnetic disk drives only.

High-speed hardware architecture for high-definition videotex system

An experimental high-definition videotex system for broadband ISDN has been developed, and this paper introduces high-speed hardware architecture for this system. Key technologies required are high-speed data transfer, and high-speed picture readout. High-speed protocol processing--using a newly developed virtual memory copy, contents rearrangement memory, two-bus architecture, and simultaneous editing and analyzing--allows a requested 6-MB picture to be displayed within 3 seconds.