Intel 7xx Servers, 170 Servers Lpar Performance Considerations, Performance on a 12-way system

The reasons for the LPAR overhead can be attributed to contention for the shared memory bus on a partitioned system, to the aggregate bandwidth of the standalone systems being greater than the bandwidth of the partitioned system, and to a lower number of system resources configured for a system partition than on a standalone system. For example on a standalone 2-way system the main memory available may be X, and on a partitioned system the amount of main storage available for the 2-way partition is X-2.

LPAR Performance Considerations

	2500
	5% increase	3% decrease
	2000	1019	1050
CPW	1950
	1500
in
Throughput	1000	1025	1050
	500
	0
	S/Alone 4-W	LPAR 2/2 W	2 x 2-W

Figure 18.1. LPAR Performance Measured Against Standalone Systems

In summary, the measurements on the 4-way system indicate that when a workload can be logically split between two systems, using LPAR to configure two systems will result in system capacities that are greater than when the two applications are run on a single system, and somewhat less than splitting the applications to run on two physically separate systems. The amount of these differences will vary depending on the size of the system and the nature of the application.

18.3 Performance on a 12-way system

As the machine size increases we have seen an increase in both the performance of a partitioned system and in the LPAR overhead on the partitioned system. As shown below you will notice that the capacity increase and LPAR overhead is greater on a 12-way system than what was shown above on a 4-way system.

IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
© Copyright IBM Corp. 2008	Chapter 18 - LPAR	296