Response Time Curve; Six-To-One Fan-Out Example - EMC Connectrix EC-1200 Planning Manual

As shown in the figure, that response time is doubled (to 2.0) when
the resource is 80% utilized. The impact on response time from the
front end into and out of cache is small as long as utilization is below
80%. Should demand from the servers exceed 80%, the system is
exposed to a very high risk of experiencing response times that
exceed the low utilization value by 50 times or more. Therefore, EMC
recommends calculating the maximum fan-out so the I/O rate does
not exceed 70% of maximum. Back-end layout is also an important
determinant of the overall system performance.
50
45
40
35
30
25
20
15
10
5
1.1
1.0
0
0% 10%

Response Time Curve

Figure 4-7
Server 1
Server 2
Server 3
Server 4
Server 5
Figure 4-8

Six-to-One Fan-out Example

Response Time Curve
Service Time = 1
Utilization = Service Time + Traffic
RT = ST / (1-Util)
1.5 1.6
1.3
1.4
50%
20% 30% 40%
Percent Utilization
Connectrix
Server 6
Connectrix Topologies
50.0
10.0
2.0
1.8 1.9
60%
70% 80% 90%
Symmetrix FA-1A
Base Switch Topologies
4
98%
4-9