IBM Power 720 Overview page 137

The knee varies depending on how compressible the memory contents are. This example
demonstrates the need for a case-by-case study of whether memory expansion can provide a
positive return on investment.
To help you do this study, a planning tool is included with AIX 6.1 Technology Level 4 SP2.
With the tool, you can sample actual workloads and estimate how expandable the memory of
a partition is and how much processor resource is needed. Any Power System server can run
the planning tool.
Figure 3-4 shows an example of the output that is returned by this planning tool. The tool
outputs various real memory and CPU resource combinations to achieve the effective
memory that you want. It also recommends one particular combination. In this example, the
tool recommends that you allocate 13% of processing power (2.13 physical processors in this
setup) to benefit from 119% extra memory capacity.
Active Memory Expansion Modeled Statistics:
-------------------------------------------
Modeled Expanded Memory Size : 52.00 GB
Achievable Compression ratio : 4.51
Expansion Modeled True
Factor Memory Size
--------- -------------
1.40 37.25 GB
1.80 29.00 GB
2.19 23.75 GB
2.57 20.25 GB
2.98 17.50 GB
3.36 15.50 GB
Active Memory Expansion Recommendation:
---------------------------------------
The recommended AME configuration for this workload is to configure the LPAR
with a memory size of 23.75 GB and to configure a memory expansion factor
of 2.19. This will result in a memory gain of 119%. With this
configuration, the estimated CPU usage due to AME is approximately 2.13
physical processors, and the estimated overall peak CPU resource required for
the LPAR is 11.65 physical processors.
Figure 3-4 Output from Active Memory Expansion planning tool
Modeled CPU Usage
Memory Gain Estimate
------------------ -----------
14.75 GB [ 40%] 0.00 [ 0%]
23.00 GB [ 79%] 0.87 [ 5%]
28.25 GB [119%] 2.13 [ 13%]
31.75 GB [157%] 2.96 [ 18%]
34.50 GB [197%] 3.61 [ 23%]
36.50 GB [235%] 4.09 [ 26%]
Chapter 3. Virtualization
123