A relatively new technique for monitoring windows servers via WMI instead of SNMP represents a measurable, but manageable, impact on both the target and the polling engine.
On a target server, monitoring with WMI plus a SAM template has no effect whatsoever on RAM or CPU, compared to simple ping monitoring. However, it represents an average increase of 12 Kbps.
The difference between WMI and SNMP polling is even less noticeable, with a 4 Kbps bandwidth bump as the only noticeable effect.
On the polling engine the impact is more pronounced. Monitoring 300 servers via WMI with a SAM template included (the most aggressive monitoring combination) results in the following increases compared to monitoring with simple “ping”:
The difference between monitoring 300 machines with WMI vs. SNMP has less of an impact on average:
If the difference between WMI and SNMP polling is statistically negligible, then why the need for additional hand-wringing? Why not just make the switch and go?
Note: The spreadsheet with the data behind this information appears as a separate upload. See here: SNMP_vs_WMI_20130410.xlsx
NPM 11.5 and earlier
The answer is that the choice of polling method has other impacts beyond the physical toll on the machines involved. Functionally, there are some pros and cons: