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

18.4 LPAR Measurements

The following chart shows measurements taken on a partitioned 12-way system with the system’s CPU utilized at 70 percent capacity. The system was at the V4R4M0 release level.

Note that the standalone 12-way CPW value of 4700 in our measurement is higher than the published V4R3M0 CPW value of 4550. This is because there was a contention point that existed in the CPW workload when the workload was run on large systems. This contention point was relieved in V4R4M0 and this allowed the CPW value to be improved and be more representative of a customer workload when the workload is run on large systems.

Table 18.1 12-way system measurements

LPAR		Stand alone	Total	CPW		LPAR CPW			Average LPAR
		12-way	LPAR
Configuration				Increase	Primary		Secondary	Secondary	Overhead
		CPW	CPW
8-way, 4-way		4700	5020	7%	3330		1690	n/a	10 %
(2)	6-ways	4700	5140	9%	2605		2535	n/a	9 %
(3)	4-ways	4700	5290	13%	1770		1770	1750	9 %

While we saw performance improvements on a 12-way system as shown above, part of those improvements may have come about because of a reduction in contention within the CPW workload itself. That is, the measurement of the standalone 12-way system required a larger number of users to drive the system’s CPU to 70 percent than what is required on a 4-way system. The larger number of users may have increased the CPW workload’s internal contention.

With a lower number of users required to drive the system’s CPU to 70 percent on a standalone 4-way system., there is less opportunity for the workload’s internal contention to be a factor in the measurements.

The following chart shows our 4-way measurements.

Table 18.2 4-way system measurements

LPAR	Stand alone	Total	CPW	LPAR CPW		Average LPAR Overhead
	4-way	LPAR
Configuration			Increase	Primary	Secondary
	CPW	CPW
(2) 2-ways	1950	2044	5%	1025	1019	3 %

The following chart shows the overhead on n-ways of running a single LPAR partition alone vs. running with other partitions. The differing values for managing partitions is due to the size of the memory nest and the number of processors to manage (n-way size).

	Table 18.3	LPAR overhead per partition
	Processors		Measured	Projected
	2		-	1.5 %
	4		3.0 %	-
	8		-	6.0 %
	12		9.0 %	-
IBM i 6.1 Performance Capabilities Reference - January/April/October 2008
© Copyright IBM Corp. 2008				Chapter 18 - LPAR	299