Storage architecture for video-on-demand systems
John C. S. Lui, Siu-Wah Lau · 1997
Recent advances in computer technologies have made it feasible to provide multimedia services, such as news distribution and entertainment, via high bandwidth networks. The storage and retrieval of large multimedia objects (e.g., video) becomes a major design issue of the multimedia information system. While most other works on multimedia storage servers assume an on-line disk storage system (2, 45, 61, 60, 76), we consider a two-tier storage architecture with a robotic tape library as the vast near-line storage and an on-line disk system as the front-line storage. Magnetic tapes are cheaper, more robust, and have a larger capacity; hence they are more cost effective for large scale storage systems (e.g., video on demand (VOD) systems (32) may store tens of thousands of videos). First, we study in detail the design issues of the tape subsystem and propose some novel tape scheduling algorithms which give faster response and require less disk buffer space. We also study the disk striping policy and the data layout on the tape cartridge in order to fully utilize the throughput of the robotic tape system and to minimize the on-line disk storage space. Third, we propose the round-robin striping approach to supporting constant display bandwidth with variable bit rate retrieval. Then, we discuss the integration of round-robin striping with a page replacement algorithm. Finally, we analyze the performance of the stream merging approach which is a novel approach for I/O demand reduction.