Managed availability, also known as Active Monitoring, or Local Active Monitoring, is the integration of built-in monitoring and recovery actions with the Exchange high availability platform. It’s designed to detect and recover from problems as soon as they occur and are discovered by the system.

Please, follow links in the end of the post to learn more about Managed Availability feature in Exchange Server, if you’re not familiar with this one.

From time to time, I stumbled upon a misunderstanding by administrators of how Managed Availability monitors work, having seen all sorts of customizations.

We will talk about 3 monitor’ properties – TypeName, MonitoringThreshold, MonitoringIntervalSeconds.

Four possible options for the value of the TypeName property are described below in the table, depending on the type, the value of the remaining 2 properties is described. In fact, TypeName defines the logic of the monitor, according to which it changes its state.

This is described in here: Managed Availability Monitors

What does it mean, let’s look at a couple of examples (one way or another I have encountered in practice).

• Disk space monitor for database and transaction logs –  Low Disk Space Monitor MailboxSpace\StorageLogicalDriveSpaceMonitor. The TypeName of this monitor is OverallConsecutiveProbeFailuresMonitor. MonitoringThreshold equals to 1.

If one last probe corresponding to the MSExchangeDagMgmt/EdbAndLogVolSpace/EachDatabase result (checking each database) identifies a problem, then the monitor goes into an unhealthy state. So, MonitoringThreshold is not the amount of disk space, neither in GB nor in %.

This threshold is hardwired into the code and is about 175GB. You can change it using the registry key HKLM\Software\Microsoft\ExchangeServer\v15\Replay\Parameters\SpaceMonitorLowSpaceThresholdInMB

After the change, you need to restart the Microsoft Exchange DAG Management service (as it is responsible for monitoring)

Described here: Monitor database availability groups

Trying to create an override for such checks like Add-GlobalMonitoringOverride -Item Monitor –Identity MailboxSpace\StorageLogicalDriveSpaceMonitor -PropertyName MonitoringThreshold -PropertyValue 50000 will not work at best (it will just increase that time for monitor to change it’s state), at worst the monitor will become healthy and the checks will simply not work. While you think that the desired monitoring threshold is set.

• Monitor Transport/STARTTLSCertificateExpiresSoon

Monitoring the expiration of the certificate (threshold – 3 months) – is done by the transport service, it has no samples, we write the event to the log. Monitor TypeName – OverallXFailuresMonitor, RecurrenceIntervanInSeconds = 300, MonitoringThreshold =1.

If one probe corresponding to the Transport/STARTLSCertificateExpiresSoon check detects a problem within 300 seconds, then the monitor enters an unhealthy state. Increasing MonitoringThreshold to a large enough value simply disables the check.

I recommend to check the overrides you’ve made 😊

More information on Manage Availability in Exchange Server:

🔗Learn more about Managed Availability

🔗Configure managed availability overrides in Exchange Server

🔗Making Managed Availability Easier to Monitor and Troubleshoot

🔗ManagedAvailabilityTroubleshooter

End.