Efficient Server Design for Hybrid Multicast Streaming - Scalable Continuous Media Streaming Systems - page 361

Zone 1
Zone 2
Zone 3
Zone 4
Zone 5
Zone 6
Zone 7
Zone 8
Zone 9
Zone 4 and 9 from a zone pair in WSGP to
accommodate data for static channels
Zone 5 and 8 from a zone pair in WSGP to
accommodate data for static channels
Zone 6 and 7 from a zone pair in WSGP to
accommodate data for static channels

Figure 20.4 Data layout for a disk with Z = 9 and Z dyn = 3

the first T R seconds of a video. Therefore, we propose replicating the first T R seconds of each
video in the outermost zones of the disk, thereby taking advantage of the higher transfer rate
of the outermost zones. Assume the first Z dyn zones are used to store the replicated video data,
then the WSGP algorithm will begin pairing zone ( Z dyn + 1) and Z . Figure 20.4 illustrates the

overall data layout.

20.4.4 An Integrated Scheduler
To support data retrievals for both static and dynamic channels, we devise a new integrated
scheduler based on the three design features previously discussed. The integrated scheduler
is still round-based but each round is divided into two parts - a static round and a dynamic
round as shown in Figure 20.5. In a static round, two continuous data retrievals are performed,
one for an outer-track block and one for an inner-track block. The retrieved data will then be
used for transmission over the static channels. The dynamic round is further sub-divided into
G D dynamic micro-rounds and the dynamic channels are then assigned to these G D dynamic
micro-rounds as in the GSS case. Retrievals within a dynamic micro-round will be executed
using SCAN and the retrieved data will be transmitted over the dynamic channels. The buffer
requirement of this scheduler is thus given by

NQ (2 N S + N D ) (20.4)

as illustrated in Figure 20.6.