Intel AS/400 RISC Server, 170 Servers, 7xx Servers manual Lpar Throughput Increase

LPAR Throughput Increase

Total Increase in CPW Capacity of an LPAR System

	5400
	5300			13%
Partitions	5200		9%
	5100	7%
all
	5000
of
CPW	4900
Total	4800
	4700
	4600
	12-way	8-way+4-way	2 x 6-way	3 x 4-way

LPAR Configuration

Figure 18.2. 12 way LPAR Throughput Example

To illustrate the impact that varying the workload in the partitions has on an LPAR system, the CPW workload was run at an extremely high utilization in the stand-alone 12-way. This high utilization increased the contention on the main storage bus significantly. This same high utilization CPW benchmark was then run concurrently in the three 4-way partitions. In this environment, the total capacity of the partitioned 12-way exceeded that of the stand-alone 12-way by 18% because the total main storage bus contention of the three 4-way partitions is much less than that of a stand-alone 12-way.

The capacity of a partition of a large system was also compared to the capacity of an equally sized stand-alone system. If all the partitions except the partition running the CPW are idle or at low utilization, the capacity of the partition and an equivalent stand-alone system are nearly identical. However, when all of the partitions of the system were running the CPW, then the total contention for the main storage bus has a measurable effect on each of the partitions.

The impact is greater on the smaller partitions than on the larger partitions because the relative increase of the main storage bus contention is more significant in the smaller partitions. For example, the 4-way partition is degraded by 12% when an 8-way partition is also running the CPW, but the 8-way partition is only degraded by 9%. The two 6-way partitions and three 4-way partitions are all degraded by about 8% when they run CPW together. The impact to each partition is directly proportional to the size of the largest partition.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
© Copyright IBM Corp. 2008	Chapter 18 - LPAR	298