Efficient Server Design for Hybrid Multicast Streaming - Scalable Continuous Media Streaming Systems - page 363

NCQ (1 + 1/ G )

Data in cache

NCQ
3NCQ/G

Buffer
requirement

2NCQ/G

NCQ/G

Time

micro-round micro-round micro-round

micro-round

service round

service round

Transmissions

Figure 20.7 Server buffer requirement when micro-rounds are of different durations (G = 4)

micro-round. Since different groups retrieve data from different zones of the disk, the static
micro-round will be of different durations.
As illustrated in Figures 20.7 and 20.8, and using derivations similar to GSS we can derive
the new total buffer requirement, which is reduced to
NQ N S 1

N D 1

1
G S

1
G D

+ + + . (20.5)

In practice, this modification can reduce the buffer requirement of static channels by as
much as 40%. In the next section we evaluate and compare performance of the proposed server
design with the GSS-based server design.

20.5 Performance Evaluation
In this section, we evaluate the performance of the presented efficient server design and com-
pare it against the GSS-based server design. Table 20.1 lists the key system parameters used in
the numerical calculations and Table 20.2 gives the specification of the disks used in perfor-
mance evaluation.