Efficient Server Design for Hybrid Multicast Streaming - Scalable Continuous Media Streaming Systems - page 355

20

Efficient Server Design for Hybrid
Multicast Streaming

This chapter investigates the issues in designing efficient media servers for hybrid multicast
streaming algorithms that integrate both closed-loop and open-loop algorithms. Existing
media server designs are either optimized for closed-loop algorithms, which generate ape-
riodic data retrievals or optimized for open-loop algorithms, which generate periodic data
retrievals. However, hybrid architectures such as the Super-Scalar Video-on-Demand (SS-
VoD) system in Chapter 19 require both periodic and aperiodic data retrievals which the
existing server designs are sub-optimal. This chapter presents an efficient server design to
address this problem, which can achieve up to 60%capacity gains compared to conventional
server designs.

20.1 Introduction
In Chapter 19 we presented a Super-Scalar Video-on-Demand (SS-VoD) architecture combin-
ing the batching, patching, and periodic broadcasting for implementing scalable and efficient
VoD services. In a SS-VoD system, multicast channels are divided into two types - static
channels and dynamic channels. Each channel transmits video data at the video playback rate
using network multicast. Static channels are organized in a time-staggered manner to stream
the whole video repeatedly and periodically. Dynamic channels are scheduled with batching
and patching to enable clients to begin playback quickly. By simultaneously caching data from
a static channel, the client can eventually merge back to an existing static channel and release
the dynamic channel for reuse by other clients.
In this chapter, we present an efficient disk-array-based server design for implementing the
video server in a SS-VoD system. The video server in a SS-VoD system is unique in that there
are both statically scheduled and dynamically scheduled video channels. Existing video servers
in general [1-5], and disk schedulers in particular [6-9], are designed either for systems with
statically scheduled video channels (i.e., open-loop algorithms in Chapter 18), or for systems
with dynamically scheduled video channels (i.e., closed-loop algorithms in Chapter 17). The