When multimedia DBMS services video data, the storage system for it needs the large disk bandwidth in order to provide more users simultaneously with the real time retrieval requests. So, the storage system of multimedia DBMS generally have the structure of disk array which consists of multiple disks. When the storage system serves multiple video stream requests, its bottlenecks come from the seeking delay caused by the random movement of disk head and from unfair disk access due to disk load unbalance among multiple disks.This paper presents a novel placement and retrieval policy for the storage system of multimedia DBMS. The new policy retrieves the requested data through sequential access and maintaining disk load balance so that it can diminish the bottlenecks on retrieving and can provide the real time retrieval services for more users simultaneously. Moreover, the novel retrieval policy introduces the concept of dummy request so that it can simply control the timing for retrieving a data.