Situations customers may face that this article covers:

• The Veeam VMware: Datastore Unknown Files Analysis monitor triggers excessive alerts.
• The Veeam VMware: Datastore Unknown Files Analysis monitor and the Scan Datastore for Unknown Files Task show different results. 
• The UnknownFilesGB metric value displayed by the Veeam VMware: Datastore Unknown Files Analysis monitor is much higher than that of the Scan Datastore for Unknown Files task.

These issues may be caused by the following situations:

• VM Migration
  A virtual machine is migrated to a new storage location. VMware vSphere keeps a copy of VM files on both the source and destination datastores until the end of the migration process. However, the VM files on the source datastore are no longer connected to the migrated VM and are reported as garbage files. This is why the UnknownFilesGB metric may show inaccurate values and alerts for the affected datastores may be triggered by the Veeam VMware: Datastore Unknown Files Analysis monitor.
  ^{Note: Veeam does not recommend using the Veeam VMware: Datastore Unknown Files Analysis monitor for datastores involved in VM migration processes.}
• Third-Party VM File Manipulation
  VM files are replicated, backed up, or copied by 3rd-party solutions without being registered on the vCenter Server side. Such files are identified by the Veeam VMware: Datastore Unknown Files Analysis monitor as files not managed by the vCenter Server. In this case, the UnknownFilesGB metric and the Scan Datastore for Unknown Files task will always show inaccurate values.
• Datastore Shared by Two vCenters
  A shared datastore is connected to two different vCenter Servers. VM files on one vCenter Server are tracked by the Veeam VMware: Datastore Unknown Files Analysis monitor, and VM files belonging to another vCenter Server are identified as unknown files. In this case, the UnknownFilesGB metric and the Scan Datastore for Unknown Files task will always show inaccurate values.

VM Migration Related

For situations caused by VM migration, consider the following:

• Increase the UnknownFilesGB parameter value specified for the Veeam VMware: Datastore Unknown Files Analysis monitor.
  ^{For more information, see the Veeam MP for VMware Operations Guide, section Overriding Performance Analysis Monitors.}
• Increase the NumSamples parameter value specified for the Veeam VMware: Datastore Unknown Files Analysis monitor.
  ^{For more information, see the Veeam MP for VMware Operations Guide, section Overriding Performance Analysis Monitors.}
• Increase the DatastoreScanInterval parameter value specified for the Collector that gathers data on datatstores involved in the VM migration process.
  ^{For more information, see the Veeam MP for VMware Operations Guide, section Collector Settings.}
  
  

When the VM migration process is over, the Veeam VMware: Datastore Unknown Files Analysis monitor may still trigger alerts in the following cases:

• The Collector has not run a new query yet, or another VM migration process has already started by the time the Collector ran the new query.
• vSphere API reports outdated datastore capacity, free space, and VM size values.
  Collectors gather data via vSphere API and calculate the UnknownFilesGB metric value using the following formula:

  unknownFilesGB = [total datastore space usage] – [free space] – [space used by known VM datastore files]
  

  
  
  

Other Considerations

If none of the cases described in this article apply, you can run the Scan Datastore for Unknown Files Task to get the list of unknown files detected on the affected datastore.

However, keep in mind that the Scan Datastore for Unknown Files task increases the load on the vCenter Server and may take a long time to complete. That is why Veeam recommends that you run this task only for those datastores reported by the Veeam VMware: Datastore Unknown Files Analysis monitor.

NOTE: As a workaround, you can disable the Veeam VMware: Datastore Unknown Files Analysis monitor for specific datastores. The Veeam VMware: Datastore Free Space Analysis monitor will continue running and reporting on free space left on those datastores.