IBM 170 Servers Manual page 224

The following charts are a view of the characteristics we observed during our Commercial
Performance Workload testing on our JS22 Express. The first chart shows the effect on the
Commercial Performance Workload when we apply 3 Dedicated processors and then switch to 3
shared processors. Then incremented the number of virtual processors available.
The "red line" is our dedicated processor set up, which is our baseline. The "blue line" is
turning on shared processors in what I might have thought of as a fair comparison where 1
virtual processor was assigned for each real processor, resulting in 1 virtual processor for VIOS
and 3 virtual processors for IBM i operating system. The Next experiment the "green line" was
to increase the number of virtual processors assigned to VIOS but not the number of virtual
processors assigned to IBM i operating system. Four virtual processors assigned to VIOS
seemed to worked best for our environment. Next was to increase the number of virtual
processors assigned to the IBM i operating system environment. Six virtual processors seen in
the "purple line" optimized our environment best. As I increased from 6 virtual processors I
started losing performance until I had increased to the 28 virtual processors available to me
shown in the "dark red line"
Not all workloads will react in the same way but it is important to note that a small change to
your configuration can have a large influence on your performance positive and negative. .
10
1
0.1
0.01
0.001
20000
DS4800 3 Dedicated Processors IBM i operating system, 1 Shared Porcessor 4 Virtual Processors VIOS
DS4800 3 Shared Processors 3 Virtual Processors IBM i operating system, 1 Processor 1 Virtual Processors VIOS
DS4800 3 Shared Processors 3 Virtual Processors IBM i operating system, 1 Shared Processor 4 Virtual Processor VIOS
DS4800 3 Shared Processors 6 Virtual Processors IBM i operating system, 1 Shared Processor 4 Virtual Processors VIOS
DS4800 3 Shared Processors 28 Virtual Processors IBM i operating system, 1 Shared Processor 4 Virtual Porcessors
VIOS
IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
©
Copyright IBM Corp. 2008
IBM i operating system JS22 Express
Commercial Performance Workload
25000 30000 35000
Chapter 14 DASD Performance
40000 45000
Transactions/Minute
50000 55000 60000
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