6.3

In the policy stress analysis seings, to examine an example graph used to calculate stress, click What is
stress?.
Another example to explain the calculation used for CPU stress is shown here.
With a peak detection window size of 60 minutes, vRealize Operations Manager calculates the CPU stress
score. It uses the area under the demand curve and above the stress threshold line as a percentage of the
area covered by the total capacity curve.
Using time stamps of t1 and t2 to identify a 60-minute window in the last 30 days, the stress score depends
on demand, stress threshold, and total capacity over time.
Maximum((Demand - Stress Threshold) ÷ (Total Capacity - Stress Threshold))
This equation applies to the stress calculations for each resource, such as memory demand, memory
consumed, and CPU demand.
If Total Capacity varies during the time range being considered, Stress Threshold must also become
variable, because (Stress Threshold) = (Stress Threshold in %) × (Total Capacity).
Since (Total Capacity) can be a dierent value at a dierent time, as identied by t, then “Stress
Threshold”(t) = “Stress Threshold in %” × “Total Capacity”(t).
As a result, the Stress score is the highest aggregate of demand that exceeds 70 percent of capacity, as a
percentage of the aggregate of capacity within any contiguous interval of 60 minutes in the last 30 days. In
formula for the score is as follows:
Maximum((Demand(t1, t2) - “Stress Threshold”(t1, t2)) ÷ (“Total Capacity”(t1, t2) – “Stress
Threshold”(t1, t2)))
Where:
n
t1 and t2 are time stamps in the time continuum within the last 30 days.
n
t1 < t2
n
t2 - t1 = 60 minutes
n
Demand(t1, t2) is the demand curve between time t1 and t2.
n
“Stress Threshold”(t1, t2) is the stress threshold curve (as absolute values) between time t1 and t2.
n
“Total Capacity”(t1, t2) is the capacity threshold curve between time t1 and t2.
vRealize Operations Manager calculates the aggregate during a contiguous time interval of 60 minutes in
the last 30 days. The Stress score is the percentage of aggregate capacity in the same contiguous time interval
of 60 minutes. An acceptable score yields a green Stress badge.
vRealize Operations Manager User Guide
78 VMware, Inc.