Multimedia storage systems store data objects and receive streams of requests from the multimedia server. When a client wishes to display an object, it sends a new object request for the multimedia object to the multimedia server as shown in Figure 15.1. The multimedia server checks to see if this new stream can be accepted. If accepted, the server sends a data request to the storage system to retrieve the first data stripe. The storage system returns the data stripe to the server. The server then encapsulates the data stripe as data packets and sends the data packets to the client. The client extracts the data stripe from the data packets. Afterwards, the server sends data requests periodically to the storage system. Each of these data requests has a deadline associated with it. If the request cannot be served before the deadline, the client program does not have any more data to display. The stream thus will be suspended or aborted. Therefore, every request of a stream, except the first one, must be served within the deadline to ensure continuity of the stream. Before we consider the scheduling methods for request streams in the next chapter, we describe the feasibility to accept concurrent streams in this chapter.
