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Using WMI Numerical Data

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Quite apart form the wealth of information available through Performance Monitor objects and counters, WMI also provides a mechanism to reach similar information and provide it to MOM.

In fact there is almost complete overlap of functionality here and there are pros and cons for using either.  WMI builds classes under the Root\cimv2\Win32_PerfRawData class to model all the available performance monitor objects and counters  on the system (Win2k and above only).   There is hardly any point in using these as they are much more simply accessed using MOM's Performance Monitor interfaces and in any case return raw data which needs complicated further processing.

Of more value is using normal WMI classes that may model numerical data.  Especially if this data changes over time.  Examples might include watching a particular Registry Key where a numerical value is stored or  periodically checking the estimated charge remaining in a UPS device (Win32_UninterruptiblePowerSupply.EstimatedChargeRemaining  if the UPS device has a WMI provider).

However there are more clear cut cases.  For example SMS records the available free space on the drive where it has installed components on a Site System.  The Administrator does not have to know which drive this is.  The information is reported in the 'Free' column of the Site System Status node in the SMS Administrator's Console.  SMS has its own mechanism to warn when space is getting low, but you have to be working on the console to see it.  Using a WMI numerical provider with MOM provides a mechanism for remote automatic monitoring.

This example show how to complete the WMI Numerical data provider dialog box:

Dialog Field	Entry	Explanation
Provider Name	Site Systems Free Space	Any name will do
WMI Namespace to be searched	root\sms\site_XXX	This is the name space used by SMS. XXX is the SMS site code.  It will only exist on the server running the sms provider.
Class of Objects to be measured	SMS_SiteSystemSummarizer	The specific class used by SMS to model the free space
Object Instance Expression	Role = 'SMS Client Access Point'	Limit the query to only site systems that are CAPs. leave this blank to see all site systems.
Numeric Property to Sample	BytesFree	The specific property of the SMS_SiteSystemSummarizer class we're interested in.
Text property to be Instance	SiteSystem	A property that identifies the server
Sample Every	1440	Every 24 hrs

Having created the provider you can incorporate it into a normal Performance Processing rule.   The result can either be a straight forward sampled output under the All Performance node where you can draw graphs, or used in a threshold comparison to generate an alert.