Much of the raw data that SolarWinds UDT polls from monitored network objects is provided initially as counter values. For example, one of the values that SolarWinds NPM polls from interfaces is ifInOctets, which returns the number of bytes the polled interface has received since the device last booted. While this value can be useful information in itself, generally, from a network performance monitoring standpoint, it is more useful to know the rate of bytes received by the interface.
In order to determine a rate, two values are required. On a new install or after a shutdown, when the SolarWinds Network Performance Monitor service starts, there is no current network data in your Orion Platform database. In this situation, by default, Orion calculates a baseline for the transmission rates of the various elements of your network. To calculate this baseline, all network resources are polled immediately upon startup, and then, as soon as the initial poll is complete, the network is polled again. The resulting two sets of data are used to calculate a nearly instant baseline view of your network performance.
If you do not need statistics immediately, or if you do not want SolarWinds UDT to calculate a baseline at startup, disable baseline calculation at startup by setting the Baseline Calculation option on the Polling Settings view to False. For more information, see Configure polling engine settings.
Baseline calculation requires significant data gathering and processing. Until baseline calculation is completed, both SolarWinds UDT server performance and the CPU performance of some of network routers may be adversely affected.