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This paper provides a data placement method based on rate staggering to store scalable video data in a disk-array-based video server. Scalable video means a video which is coded in such a way that subsets of the full video bit stream can be decoded to create low quality/resolution videos. Supporting layered multiple resolutions from a video server is very desirable in many applications. Note that in a disk array the video data corresponding to different rates of the same video clip are not required to reside in the same disk. In view of this, we propose and explore in this paper the approach of rate staggering, i.e., staggering video data in the disk array based on data rates, it is shown that the advantages of the proposed rate staggering method include: (1) minimizing the intermediate buffer space required by the server, (2) achieving better load balancing due to finer scheduling granularity, and (3) alleviating the disk bandwidth fragmentation. These advantages enable a video server using the rate staggering method to provide feasible solutions to some video stream requests which cannot be met otherwise. The system throughput can thus be increased. We also conduct several simulations for various applications. These experimental results show that the rate staggering method can significantly improve the performance of a VOD system.