Solutions > Viewing Polling Engine Status > Calculating Node Availability and Calculating a Baseline

Calculate node availability

The Availability Calculation setting on the SolarWinds Polling Settings view provides a choice between the following two methods for determining device availability.

Node Status

The default method is based upon the historical up or down status of the selected node. The selected node is polled for status on the Default Node Poll Interval defined on the SolarWinds Polling Settings view.

If the selected node responds to a ping within the default interval, the node is considered up, and a value of 100 is recorded in the Response Time table of the Orion database. If the node does not respond to a ping within the default interval, the node is considered down and a value of 0 is recorded in the Response Time table of the Orion database. To calculate node availability over a selected time period, the sum of all Response Time table records for the selected node over the selected time period is divided by the selected time period, providing an average availability over the selected time period.

Percent Packet Loss

The second method is a more complicated calculation that effectively bases the availability of a selected node on its packet loss percentage. As in the Node Status method, the selected node is polled for status. If it responds within the Default Node Poll Interval defined on the SolarWinds Polling Settings view, a value of 100 is averaged with the previous 10 availability records.

The result of the Percent Packet Loss calculation is a sliding-window average. To calculate node availability over a selected time period, the sum of all results in the Response Time table for the selected node over the selected time period is divided by the selected time period, providing an average availability over time.

Note: The Percent Packet Loss method introduces a historical dependency into each availability node record. In general, it is best to leave calculations based on Node Status unless you specifically need node availability based on packet loss.

Calculating a Baseline

Much of the raw data that SolarWinds SAM polls from nodes is provided initially as counter values. If you do not need statistics immediately, or if you do not want SolarWinds SAM to calculate a baseline at startup, disable baseline calculation at startup by setting the Baseline Calculation option on the SolarWinds Polling Settings view to False.

Baseline calculation requires significant data gathering and processing. Until baseline calculation is completed, both SolarWinds SAM server performance and the CPU performance of some of network routers may be adversely affected.

For more information, see Adjust threshold settings and apply baseline data.