I had a question asked today which wasn’t necessarily intuitive so it seems like a good one to write-up. The question was what the thresholds are for Operations Manager to provide an free disk space alert on a drive. From a high level this sounds simple as there are hard-coded thresholds which exist as part of the management. For this situation we had a non-system drive on a server which was low on space and the question was asked about why it was not alerting due to low disk space.

Question: How do I determine what the thresholds are for a specific drive in my OpsMgr environment?

Answer: In the OpsMgr console these can be found relatively quickly by opening the Monitoring / Microsoft Windows Server / Logical Disk State, and filtering by the name of the server.

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From this view, right-click on the drive in question and open the Health Explorer.

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In Health Explorer open the Entity Health / Availability / Logical Disk Free space and right-click and open the Monitor properties.

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There are two settings which are defined for the free disk space alert (% and MBytes). OpsMgr does not alert unless both conditions are true. Each of these thresholds are configurable but the default configurations are:

System Drive:

Critical at 5% free disk space and < 100 mb

Warning at 10% free disk space and < 200 mb

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Non-System Drive: (as in this example)

Critical at 5% free disk space and < 1000 mb

Warning at 10% free disk space and < 2000 mb

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For our example this server is set to default configuration for a non-system drive which is:

Critical at 5% free disk space and < 1000 mb

Warning at 10% free disk space and < 2000 mb

These thresholds can be changed on a per-drive level, on a group level or for all drives through the Overrides tab for the Monitor. When checking the actual settings for the drive use the Overrides tab as it will display what the current values are for the specific drive that you are viewing including what overrides may have been created that apply to it.

Since our server has approximately 3.5% free disk space and 3031 mb (approximately) of free space it is not generating an alert. This is because only one of these two conditions are correct. Once the free disk space is under 2000 it will go to warning, and at under 1000 mb it will go to critical.