The Agent brings back Raw Data for the Performance Counters
Can the Agent retrieve the Formatted Data for Performance Counters?
The Performance Counters administration screen allows for the configuration of custom performance counters and their units of measure. The custom performance counters are accessible via the User Metrics drilldown. The Performance Counters administration screen is used for adding custom collections of performance counters to a specified agent by selecting them from the complete list of available performance counters. The performance counters value refers to raw data, which is derived directly from the counter provider.
The Agent, by default, will retrieve only the Raw Data values for Windows performance Counters. This is because formatted values make sense only if the collection frequency is set to 1 second (as in Perfmon). Frequency of 1 second is not reasonable in Foglight, performance wise: Via the raw counters once can get an accurate picture for the sample period.
The usage of Raw Data in the Agent yields with most customer requirements and aligns with the sample periods. If additional information is required, then a customization can take place. For example, on top of the raw data, the user can create custom (derived) metrics that reflect the activity of the sampling period.
So for example, in order to calculate CPU usage:
CPU usage is : (1 - (N1-N0)/(D1-D0))*100
In the example above (see Notes below for more details):
Or, in other words:
If you take the PercentProcessorTime from two consecutive samples and calculate the delta, then transform the sample period to 100ns units and the ratio between these two deltas is the CPU consumption. Hence:
This reference from Microsoft mentions the requirement for processing the raw data classes:
On raw data classes, your [script] must perform calculations to obtain the same output as Perfmon.exe.
The algorithm used for processing these raw data counters depends on counter type as explained here.
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