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Disk Free sensor shows "Could not convert variant of type (Null) into type (String)"

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When adding the WMI Disk Free sensor to a Windows 2008 server (64bit) device it shows the error message "Could not convert variant of type (Null) into type (String)". Other WMI sensors are working for this device and the same sensor is also working on other devices.

What could be the problem?

disk-free prtg wmi

Created on Aug 31, 2010 1:31:27 PM by  ehaver (0) 1



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Hello,

this is unfortunately a bug in PRTG, but will be fixed with PRTG 8. Please bear with us. In the meanwhile please consider using WMI Volume Sensors.

Best Regards.

Created on Aug 31, 2010 1:34:34 PM by  Torsten Lindner [Paessler Support]



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When I configure the WMI Volume Sensors for this VM (VMWare) it discovers three volumes of which one, the E volume, is a CD-drive that gives the above conversion error. The C volume sensor works properly but the D volume sensor gives the following error: Invalid data (code: PE025).

Created on Sep 1, 2010 5:53:31 AM by  ehaver (0) 1



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Hello,

please use our WMI-Tester to scan against the target with the following Query:

Select DeviceID, FreeSpace,Capacity FROM Win32_Volume

For any drive that delivers empty fields in "Capacity" or "FreeSpace" then the message from PRTG would be correct.

Created on Sep 1, 2010 4:29:11 PM by  Torsten Lindner [Paessler Support]

Last change on Aug 27, 2013 7:53:54 AM by  Konstantin Wolff [Paessler Support]



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I ran this query and the FreeSpace nor the Capacity is empty for drive D. I have selected drive D for the WMI disk free sensor but the following error message "Could not convert variant of type (Null) into type (String)". For drive C it did work.

Created on Sep 6, 2010 12:58:44 PM by  ehaver (0) 1



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Would it be possible for you to setup a PRTG 8 beta Testsystem that scan the exact same host with a WMI Disk Free Sensor? The Problem should not appear then. You could use a trial license for the beta-test, so you don't need to take "any risks" on the PRTG 7 Production system of yours.

Created on Sep 6, 2010 3:14:21 PM by  Torsten Lindner [Paessler Support]

Last change on Sep 6, 2010 3:15:08 PM by  Torsten Lindner [Paessler Support]



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Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.