HP Capacity Advisor 7.2 User Guide

• A move from one system architecture to another system architecture can increase or decrease
resource utilization.
• A move from a two-way to a one-way system can decrease resource utilization.
• A change in the application can increase or decrease resource utilization.
(For information on how utilization is calculated for each resource, see Appendix (page 211).)
Memory multiplier
Meaning
The ratio of change in memory utilization due to using a different platform (PA-RISC, Itanium, or
Xeon, for example) to host workloads in the scenario than the platform originally assumed. If
changes made in a scenario assume using the same platform, use the default multiplier.
Default
The default value is 1.0 (0% change)
Where you might use this multiplier
• when moving workloads from one system architecture to another different system architecture
in a scenario.
Simple examples
If you are moving from:
• PA-RISC to PA-RISC: keep the value as 1.0 (no change).
• PA-RISC to Itanium: because Itanium has 64-bit addressing, you may expect a decrease in
memory utilization. Use .5 to arrive at a 50% decrease in utilization.
Detailed example
Assume that you benchmark your current application on a test machine that is similar to one that
is currently running a production application. Assume that the test machine is a two-way 550 MHz
PA-RISC system with a benchmark of 400 CPU seconds to complete, using 400 MB of RAM.
Next, assume that you want to run a newer version of the application on a one-way, 1.6 GHz,
HP Integrity Virtual Machine. Your new benchmark for this application is 100 CPU seconds to
complete, using 600 MB of RAM.
To compute the Memory Multiplier, calculate the ratio of the memory used for the new and the old
platform:
600/400 = 1.5
The multiplier of 1.5 represents a 50% increase in memory utilization.
This change is affected primarily by the move to Integrity and by getting a new version of the
software application. In the case of memory utilization, factors like the number of CPU cores and
the use of virtual machines have no effect unless the application tests for these factors and changes
its behavior accordingly.
To return to a planning checklist:
• Obtaining reports on current resource usage (page 131)
Adjusting for change in a workload
The following sections describe the multipliers that you can use when you create new workloads.
The multipliers help you to more accurately simulate changes in resource demand that are anticipated
for workloads in a new data center configuration.
TIP:
These workload multipliers are also available to use when editing a simulation that represents a
real workload in your data center. However, in this situation, you will achieve more accurate
predictive results if you use forecasting growth rates to model anticipated change in an existing
workload.
184 Calculation assistance