HP Labs Technical Reports

A Novel Video Layout Strategy for Near-Video-on-Demand Servers

Chen, Shenze; Thapar, Manu

HPL-97-52

Keyword(s):Near-Video-on-Demand; video server; multimedia

Abstract: Near-Video-on-Demand (NVOD) provides customers with a service model completely different from true Video-on-Demand (VOD). In the NVOD service model, customers' requests are not serviced immediately. NVOD servers typically support limited VCR functions. Since the NVOD service needs to be much cheaper than the VOD service, it is important to minimize the server's cost. In this paper, we present a novel video layout strategy for NVOD servers that enforces sequential disk access. Thus, the disk bandwidth is optimally utilized. We define a model that analyzes the storage subsystems behavior, buffer requirements, and usage. Strategies that match the actual disk bandwidth to the application bandwidth requirements are developed. Using this layout strategy, each disk can deliver 50% more streams than can a VOD system, and memory buffers are reduced by almost half. Since disks and memory account for a significant portion of the total system cost in a video server, using these strategies significantly reduces server costs. From this layout strategy we further derive two other layout strategies, Segment-Group-Pairing (SGP) and Disk- Pairing (DP), both of which are designed to optimize disk bandwidth usage. The circumstances and conditions under which these two strategies work best are described. Finally, an experimental NVOD server prototype was built that supports both "broadcast" and "on-demand" service models. Using this prototype, we achieved our design and performance objectives and have demonstrated that our proposed layout strategies are practical.

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