In this paper, we propose a RAID-disk placement algorithm of coded video data and an efficient disk prefetching method to increase the number of clients who can be serviced interactive operations in the media server. Our placement policy is incorporated with a special bit count control method that is based on repeated tuning of quantization parameters to adjust the actual bit count to the target bit count. The encoder using this method can generate coded frames whose sizes are synchronized with the RAID stripe size, so that when various fast-forward levels are accessed we can reduce the seek and rotational latency and enhance the disk throughput.