PRTG Manual: Probe Health Sensor

Sensor creation

• PRTG automatically creates this sensor. You cannot delete it.

Probe device

• You can create this sensor only on a probe device.

Performance impact

• This sensor has a very low performance impact.

Limits

• This sensor has predefined limits for several metrics.

• PRTG dynamically creates limits for the Data Storage Free channel of this sensor.

Knowledge Base

• Knowledge Base: My probe system is running out of disk space. What can I do?

Primary Channel

Select a channel from the list to define it as the primary channel. In the device tree, PRTG displays the last value of the primary channel below the sensor's name. The available options depend on what channels are available for this sensor.

You can set a different primary channel later by clicking below a channel gauge on the sensor's Overview tab.

Graph Type

Define how this sensor shows different channels:

• Show channels independently (default): Show a graph for each channel.
• Stack channels on top of each other: Stack channels on top of each other to create a multi-channel graph. This generates a graph that visualizes the different components of your total traffic.
  You cannot use this option in combination with manual Vertical Axis Scaling (available in the channel settings).

Stack Unit

This setting is only visible if you select Stack channels on top of each other above.

Select a unit from the list. PRTG stacks all channels with this unit on top of each other. By default, you cannot exclude single channels from stacking if they use the selected unit. However, there is an advanced procedure to do so.

Data Storage Free

The free disk space on the probe system

PRTG dynamically creates limits for this channel. This means that Enable alerting based on limits is enabled in the channel settings but the limits are empty. Because of this, you cannot save any changes to the channel settings. Enter limits or select Disable limits to save changes to the channel settings.

Downtime

In the channel table on the Overview tab, this channel never shows any values. PRTG uses this channel in graphs and reports to show the amount of time in which the sensor was in the Down status

Handles

The counter for the data structures of the operating system. It is responsible for internal resource management. Investigate obviously increasing values that occur repeatedly.

Health

The sum of the probe state as a value between 100% (healthy) and 0% (failing). Investigate frequent or repeated health values below 100%.

This channel is the primary channel by default.

Interval Delay non-WMI&SNMP

The interval delay in percent for all sensors that are not of the type SNMP or WMI. If this value is above 0%, try to increase the scanning intervals or distribute your sensors among probes.

This channel has default limits:

• Upper error limit: 100%
• Upper warning limit: 50%

Interval Delay SNMP

The interval delay in percent for SNMP sensors. If this value is above 0%, there are probably too many SNMP v3 sensors that are very slow. In this case, try to increase the scanning intervals or distribute the sensors among probes.

This channel has default limits:

• Upper error limit: 100%
• Upper warning limit: 50%

Interval Delay WMI

The interval delay in percent for WMI sensors. If this value is above 0%, WMI sensors were not able to check the target device according to their interval. 100% means that WMI sensors are checked with twice their interval on average. For values above 0%, try to increase the scanning intervals or distribute the sensors among probes to keep the number of WMI sensors per probe below 120 (with a 60-second scanning interval) or 600 (with a 300-second scanning interval).

This channel has default limits:

• Upper error limit: 100%
• Upper warning limit: 50%

Lost Flow Packets

The number of lost Flow packets. The higher this value, the less flow packages PRTG can handle. Usually, this value should be 0%. Investigate increasing values.

This channel has default limits:

• Upper error limit: 10%
• Upper warning limit: 1%

Memory Usage

The amount of memory that is used by the PRTG probe service as reported by the memory manager. Investigate obviously increasing values that occur repeatedly. If the value is constantly above 2 GB, this indicates that PRTG runs at its limits. In this case, you should distribute some sensors among remote probes.

This channel has default limits:

• Upper error limit: 3221225472 bytes
• Upper warning limit: 1610612736 bytes

Message Queue

The number of monitoring results that have not been processed by the PRTG core server yet. This value should usually stay below 1/10 of the sensor count.

Open Requests

The number of active monitoring requests. This value should stay below the maximum of 500 open requests.

This channel has default limits:

• Upper error limit: 400

• Upper warning limit: 100

Probe Process CPU Load

The CPU load (%) that the probe process causes. Extensive CPU load can lead to false, incomplete, and incorrect monitoring results. This value should usually stay below 50%.

Syslog Buffer

The number of buffered syslog packages. Usually, this value should be 0 (or very low). Investigate increasing values.

Syslog Drop

The number of dropped syslog packages

Threads

The number of program parts that are running simultaneously. This value can increase with heavy load. Usually, the number should not exceed 100.

This channel has default limits:

• Upper error limit: 1400
• Upper warning limit: 1000

Toplist Memory

The amount of RAM that the Toplists on this probe are using. Stay below 1 GB memory usage (depending on the available memory on the probe system). If necessary, reduce the number of Toplists or distribute them among probes.

This channel has default limits:

• Upper error limit: 2147483648 bytes
• Upper warning limit: 1073741824 bytes

Trap Buffer

The number of buffered SNMP traps. Usually, this value should be 0 (or very low). Investigate increasing values.