HP Capacity Advisor 6.2 Users Guide

Network I/O The maximum capacity for network I/O defaults to the high-water mark (that is,
the maximum observed or collected value) for network I/O. However, to set the upper bound
to a value you choose, select Configure→Edit Network and Disk I/O Capacity... from the
Visualization tab in Virtualization Manager.
Disk I/O The maximum capacity for disk I/O defaults to the high-water mark (that is, the
maximum observed or collected value) for disk I/O. However, to set the upper bound to a value
you choose, select Configure→Edit Network and Disk I/O Capacity... from the Visualization
tab in Virtualization Manager.
Power Expected maximum and minimum power values for systems and workloads are
computed using the CPU and power utilization data collected from HP Insight Control power
management (IPM). However, these values can also be set manually from the Virtualization
Manager menu bar (select Configure→Calibrate P ower (All Selected Systems)...) for specified
systems; or from the Capacity Advisor Edit Scenario: System tab menu bar (select
Edit→Calibrate Power (All Selected Systems)...) for a specific scenario.
Measuring and analyzing resource utilization
In using Capacity Advisor, it is helpful to understand how the tool approaches sampling and
data analysis, and the user-provided information that affects these.
Peaks and sums
Measuring utilization of computing resources is more complex than simply determining the
maximum memory or processor utilization.
Sum of peaks An old standby in capacity planning is to simply take the peak of the two loads
and use that to determine the maximum required capacity; this is the “sum of peaks”. While this
will definitely provide a robust solution, it does not take into account the timing of the peak of
the loads and may end up planning for more capacity than is actually used.
Peak of sums A more efficient planning solution, which is easily accomplished using HP Insight
Capacity Advisor software, takes into account the timing of the maximum utilization peaks in
the individual loads. By adding together utilization at each measured interval and then taking
the maximum of the resulting time sequence, a more accurate measure of the required maximum
resource can be determined. This can lead to cost savings when planning the resources required
to consolidate loads onto new or existing servers.
Sampling interval
Where used, the Utilization Provider runs on each monitored system to collect information on
resource utilization. At the CPU-clock cycle level, a processor is either busy or idle. For Capacity
Advisor, the average utilization for each 5-minute (300 seconds) interval is stored. Therefore,
peaks lasting less than 5 minutes are not visible.
Because each data point is the average of the five preceding minutes of values, this averaging
tends to flatten the graphs, particularly when compared with real-time graphs in which each
data point is the average of values from the 15 preceding seconds.
For data collected using an agentless solution, collection intervals can vary depending on values
that you set and the number of machines in the collection.
Headroom
Headroom is the difference between the observed utilization on a system and the maximum
available capacity. That is, the headroom of a system is the amount of additional capacity that
can be used without violating the utilization limits of the applications running on that system.
For example, if you have a system with 4 cores where you never want utilization to exceed 75%,
and peak utilization is 1.75 cores, then headroom is 1.25 cores.
Measuring and analyzing resource utilization 25