Storage Replication and Layout in Video-on-Demand Servers


We propose and analyze an architecture for storage servers in large Video on Demand (VoD) systems. We describe a method for distributing the collection of titles among the levels of the storage hierarchy, based on estimates of the mean demand for each title. The resulting distribution minimizes cost for a given level of performance. Since high availability is desirable in VoD systems, we consider the use of mirroring or parity-based redundancy ({\it \`a la} RAID) and estimate the effect on the system's cost and availability. In the very-large-scale storage systems needed for VoD, the placement of disk arrays on the pool of computers must be chosen carefully to provide high availability for the least cost. We propose a strategy for arranging disk arrays on a pool of PCs; our strategy is inspired by Holland and Gibson's work on parity declustering for RAID.
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