Knowledge Base

Details about the meaning of the "Busy Sensors" value in PRTG Traffic Grapher

While you are using the Windows GUI of PRTG you will see a "Busy Sensors" value in the status bar. Under larger installations or installations with small intervals you should keep an eye on this value.

The maximum number of SNMP sensors that you can monitor with PRTG depends - apart from other aspects - on the latency of the devices that you want to scan (=the time it takes a device to answer the SNMP requests from PRTG). Especially if a larg number of SNMP requests fail and cause a timeout (due to devices being powered off, packet loss in your network and failing data lines) the "busy sensors" value can jump to high values.

As of version 6.0.6.x, PRTG has an internal limit of 300 concurrently busy sensors (previous V6 verisons had a limit of 100, whereas there was no defined limit for V5 versions). Under normal usage the busy sensors value should always be much smaller on your system.

The busy sensors value should be below 150 for normal use. Values above 250 are critical because this means that not all sensors can be monitored within the desired intervals. If the value 300 is reached all pending sensors are halted until one of the 300 busy sensors is finished, then one of the halted sensors is executed.

The following interval values are a rough guide based on real-world experiences. But for a specific network the values can be quite different. Only a test will show the real values for your network. 

Less than 100 sensors: Recommended minimum interval of 5s
Less than 500 sensors: Recommended minimum interval of 30s
Less than 1000 sensors: Recommended minimum interval of 60s
Less than 3000 sensors: Recommended minimum interval of 120s

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PRTG Traffic Grapher V6

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