“The page below is from the manual of PRTG,
our quick-to-install and easy-to-use network monitoring software”

Aurelio, System Admin at Paessler AG

Windows Management Instrumentation (WMI) is Microsoft's base technology for monitoring and managing Windows based systems.

How WMI Works

WMI allows accessing data of many Windows configuration parameters, as well as current system status values. Access can be local or remote via a network connection. WMI is based on COM and DCOM and is integrated in Windows 2000, XP, 2003, Vista, 2008, and Windows 7 (add-ons are available for Windows 9x and NT4). PRTG officially supports WMI for Windows XP or later.

In order to monitor remote machines, PRTG's WMI sensor needs Active Directory account credentials to have access to the WMI interface. You can enter these credentials in PRTG for the parent device or group, or in the Root group. The sensor will then inherit these settings.

For an overview and details about all WMI sensors, please see the List of Available Sensor Types section.

Limitations of WMI on Windows Vista and Windows Server 2008 R1

You should be aware that performance of WMI based monitoring is drastically limited when the monitoring station or the monitored client runs on Windows Vista or Windows Server 2008 R1. When it comes to network monitoring via WMI, Windows XP and Windows 2003 are up to 70 times faster than Windows 2008 or Vista.

Note: These are not limitations of PRTG, but arise from the WMI functionality built into the Windows operating systems mentioned.

The results of our tests are:

  • On Windows XP/Windows 2003/Windows 7/Windows 2008 R2 you can run about 10,000 WMI sensors with one minute interval under optimal conditions (such as running the core and the target systems exclusively under Windows 2003 and being located within the same LAN segment). Actual performance can be significantly less depending on network topology and WMI health of the target systems - we have seen configurations that could not go beyond 500 sensors (and even less).
  • On Windows Vista/Windows 2008 R1 you can run about 300 WMI sensors with one minute interval.
  • The more Windows Vista/Windows 2008/Windows 7 client systems you have in your network the more WMI monitoring performance will be affected.
  • System performance (CPU, memory etc.) of virtualization does not strongly affect WMI monitoring performance.

If you want to use WMI for network monitoring of more than 20 or 30 systems, please consider the following rules:

  • Do not use Windows Vista or Windows 2008 R1 as monitoring stations for WMI-based network monitoring.
  • If possible use Windows 2003 R2 Server for WMI based network monitoring (followed by XP and Windows 7/2008 R2).
  • If you cannot run PRTG on Windows XP/Windows 2003 consider setting up a remote probe with XP for the WMI monitoring. (You still get far better WMI monitoring performance with a remote probe on a virtual machine running Windows XP or Windows 2003 than on any bare metal system running Windows Vista/Windows 2008 R1.)
  • Consider switching to SNMP-based monitoring for large networks. Using SNMP you can easily monitor 10 times as many nodes as with WMI (on the same hardware).
     

More

Knowledge Base: General introduction to WMI and PRTG

 

Tool: Paessler WMI Tester. A useful freeware tool to test WMI connections. Tests the accessibility of WMI (Windows Management Instrumentation) counters in a quick and easy manner.

 

CEO's Blog: Don't Use Windows Vista And Windows 2008 R1 for Network Monitoring via WMI!

 

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