By default, the sampling interval for metrics shown in graphs and tables is set to 5 minutes. To use a different sampling interval, select a corresponding entry from the Sample Interval drop-down list in the device performance toolbar (e.g., 1 minute, 5 minutes, 30 minutes, 1 hour, 6 hours, 12 hours, 1 day). All graphs in the device performance page will be updated to show data in the selected sampling interval.
The sampling interval determines the granularity of the data shown, i.e., how many bars in graphs or lines in tables are shown per given time period. For example, if the time period is set to Last 60 minutes, and the sample interval is set to 5 minutes, the graphs will display 12 bars within one hour interval (60/5=12). The graph bars and values in tables display the average values within the sampling intervals.
Note: About data aggregation and values displayed
For all metrics shown in device performance web pages (e.g., response time, CPU load, interface utilization, MOS, etc.) the collected values are being gradually aggregated, meaning that from individual readings, average values are being calculated and displayed in graphs and tables, depending on the time period and the sampling interval set.
By default, the following aggregation model is used for performance data (a different aggregation model is used for NetFlow data):
* The values for the last 7 days are kept unmodified in the database (raw data without aggregation).
* For the period between the last 32 days and last 7 days, only the hourly averages are kept in the database.
* For the period between the last 366 days and last 32 days, only the daily averages are kept in the database.
The graph bars and table values in device performance web pages always display the average values of readings within sample intervals, for example, if the polling interval is 1 minute and the sampling interval is 5 minutes, then each graph bar and table value will show the average value of 5 readings (approximately). By setting the sampling interval to equal to or less than polling interval (for any period within the last 7 days for which the raw data is kept by default), one can view the actual raw data (individual readings collected from devices).
In addition to average values, the absolute maximum (MAX) and minimum (MIN) values are shown in graphs and tables for each sampling interval.