System Center Operations Manager has many talents. And the one I like most of all is its ability to bring surprises every day. Today’s surprise is how it delivers performance data to the user. If you know a lot about SCOM architecture, it will not take long to understand and absorb SCOM’s specialties. If not – you’ll be surprised :).
Most users think that there are two ways to get performance data collected by SCOM:
That’s wrong. There are three ways:
- Console – performance view
- Console – performance widget
Why three? Because performance views and performance widgets are different. Very different.
Difference #1: data source
SCOM writes collected data into 2 (two) databases – operational database and data warehouse. SCOM Performance view consumes data from the operational database, so you always get raw data. Performance widget is different – it consumes data from (surprise!) SCOM data warehouse.
Difference #2: aggregation
What? Aggregation in console? Yes! Performance view deal with raw data only, so when you try to view data for a long period of time, you get many samples. Long time range – many data points. Short time range – not-so-many data points. That’s it. Simple.
Performance widget is different. Take a look at the signature of SDK.Microsoft_SystemCenter_Visualization_Library_SinglePerformanceDataSeriesGet stored procedure in the data warehouse, and you will find a @NumberOfDataPoints parameter. Performance widget always requests 100 data points and expects to get 100 data points. So, if there are too many data points within the selected time range, the stored procedure will do “reduction” (i.e. re-aggregation) or will switch to hourly-aggregated values. Or it will do both. In the worst case, you’ll get daily aggregated values plus reduction.
Illustrations: SCOM Performance View vs. SCOM Performance Widget
Some performance counter, performance view, 8 hours:
Same performance counter, performance widget, 8 hours (looks alike):
Same performance counter, performance view, 24 hours:
Same performance counter, performance widget, 24 hours (looks very different):
SCOM Performance View and Performance Widget behave differently if the number of data points to be drawn is greater than 100. Is that a bug? Absolutely not. That is a feature which allows you to do some historical research right in the console. Just be aware of this behavior and keep in mind that you do not need to go for reporting if you need performance data for a long time range.