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10
A Concurrent-Push Parallel
Server Architecture
This chapter presents and analyzes the performance of a concurrent-push parallel server
architecture for building high-capacity streaming servers from many low-cost commodity
servers. The architecture adopts server striping for load balancing and extends the server-
push servicemodel for use in the parallel-server architecture. This architecture is particularly
suitable for deployment in networks that support resource allocation and QoS control as
the data flows generated from the servers have a constant data rate. This architecture can
potentially be scaled up to more than ten thousand concurrent streams.
10.1 Introduction
In this chapter, we investigate a concurrent-push parallel server architecture for designing
scalable media streaming systems such as video-on-demand (VoD) systems. We employ server
striping to achieve load sharing across multiple servers without requiring the additional storage
overhead incurred in replication. Furthermore, by striping using a small unit size, the system is
insensitive to skewness in the videos' popularities. This architecture allows one to incrementally
scale up the system capacity to more concurrent users by adding (rather than replacing) more
servers and redistributing (rather than duplicating) video data among them.
In the following, we present and analyze quantitatively the concurrent-push scheduling
algorithm for scheduling disk retrieval and network transmission in parallel video servers. We
show that a simple extension of the server-push servicemodel for parallel video servers does not
perform well and introduce an Asynchronous Grouped Sweeping Scheme (AGSS) to improve
the system performance. Next, we present a Sub-Schedule Striping (SSS) scheme to further
increase the scalability of the architecture. Using numerical results with realistic assumptions,
we show that the resultant architecture can be scaled up to more than ten thousand concurrent
users.
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