Storage systems for movies-on-demand video servers

We evaluate storage system alternatives for movies-on-demand video servers. We begin by characterizing the movies-on-demand workload. We briefly discuss performance in disk arrays. First, we study disk farms in which one movie is stored per disk. This is a simple scheme, but it wastes substantial disk bandwidth, because disks holding less popular movies are underutilized; also, good performance requires that movies be replicated to reflect the user request pattern. Next, we examine disk farms in which movies are striped across disks, and find that striped video servers offer nearly full utilization of the disks by achieving better load balancing. For the remainder of the paper, we concentrate on tertiary storage systems. We evaluate the use of storage hierarchies for video service. These hierarchies include a tertiary library along with a disk farm. We examine both magnetic tape libraries and optical disk jukeboxes. We show that, unfortunately, the performance of neither tertiary system performs adequately as part of a storage hierarchy to service the predicted distribution of movie accesses. We suggest changes to tertiary libraries that would make them better-suited to these applications