The CANDID Video-on-Demand Server

Abstract

The paper presents a simulation study of CANDID, a video-on-demand server. CANDID is distributed, scalable, cost-efficient server capable of providing service to hundreds or thousands of clients. The server consists of several processing nodes with several disks each, connected in shared-nothing manner. Compressed movies are declustered across all disks of the server. Movies are read by fragments of equal play-back time rather than by fragments of equal size as in traditional systems. Knowledge of fragment lengths allows accurately estimating deadlines for requests. We design a new real-time disk scheduling algorithm that emphasizes delivering video fragments close to their deadlines. The performance of CANDID is compared against the performance of SPIFFI, the advanced system based on a traditional approach. The comparison demonstrates that the new fragment delivery schema and disk scheduling algorithm substantially reduce memory requirements on both the server and clients. The interac..