Adding Subclient Content Using Discovery Rules (Microsoft Hyper-V)

You can define discovery rules to automatically assign virtual machines to subclient content. This feature is useful in environments where virtual machines are added, removed, or relocated frequently, or when you want to manage groups of similar virtual machines by using different subclients.

You can also add the subclient content by browsing and selecting the virtual machines, hosts, or volumes. For more information on adding subclient content using browse, see Adding a User-Defined Subclient.

Rules for automatic selection can be defined based on the following criteria:

  • Virtual machine name or pattern
  • Server hostname
  • Operating system group
  • DNS hostname
  • Power State
  • Notes

You can also define a combination of rules to discover virtual machines.


  • If you browse and add the VM display name to the discovery rule, the discovery is performed based on the GUID of the VM. Later, when you restore the VM in place from a backup, a new GUID is generated for the VM and the VM is no longer included for backups. To include the restored VM in the backups, you must remove the old content rule, then add a new rule, or use a name pattern for the virtual machine.
  • If you change the GUID when migrating the VM from one storage location to another, the discovery rule does not recognize the migrated VM and therefore the VM is not included in the subclient content for backups.

    To back up the migrated VM, do one of the following:

    • Maintain the same GUID when migrating the VM.
    • If you change the GUID, add the VM to the subclient content manually after the migration is complete.

Missing Content

If an automatic discovery rule for a subclient identifies an entity that cannot be found, a backup job for the subclient fails. For example, if a rule points to a host that has been retired, the inability to find a host is treated as a failure during discovery, and the backup job fails.

  • To enable backup jobs to continue when an entity is not found, add the bAllowMissedContent additional setting on the Virtual Server Agent proxy and set the value to true.
  • To generate a warning message when a content entity or rule does not return any results, add the bWarnEmptyContentRule additional setting on the Virtual Server Agent proxy and set the value to true.
  • Backup jobs for the default subclient complete successfully if no virtual machines are discovered for the default subclient. To change this behavior, configure the AllowEmptyDefaultSubclient additional setting on the Virtual Server Agent proxy and set the value to false.
  • To enable backup jobs for non-default subclients to complete successfully when no virtual machines are discovered for non-default subclients, configure the AllowEmptySubclient additional setting on the Virtual Server Agent proxy.

    To the VSA proxy computer, add the AllowEmptySubclient additional setting as shown in the following table.

    For instructions about adding additional settings from the CommCell Console, see Adding or Modifying Additional Settings from the CommCell Console.











Before You Begin

Review the following requirements:

  • If you want to define rules based on guest OS or guest DNS hostname, ensure that following prerequisites are satisfied:
    • The virtual machine must be powered on at the time of the backup.
    • The Hyper-V integration services must be installed and updated on the virtual machine.


  1. From the CommCell Browser, expand Client Computers > virtualization_client > Virtual Server > Hyper-V > backup_set.
  2. Right-click the subclient, and then click Properties.
  3. In the Subclient Properties dialog box, click the Content tab.
  4. Define a rule:
    • In the Rule Group box, select the rule type from the drop-down list and enter the appropriate information in the box on the right:

      Note: You can also use wildcard characters when defining rules based on a name or pattern.

      Rule name


      VM Name/Pattern

      Enter a pattern. For example, to identify VMs for which the VM name begins with "Test", enter Test*.

      Note: If a VM is added to subclient content using a specific name (without wildcards), and the software cannot find the VM based on that name during a backup job, the backup job completes with the error: Virtual machine [VMName] was not found.


      Enter the host name as it appears in the Hyper-V host. When you add a host, all virtual machines on the host are included in the backup.

      Guest OS

      Enter the exact name of the operating system or a pattern to identify an operating system group.

      For example,  to identify any virtual machine that has a version of the Windows operating system, enter Microsoft*.

      Tip: To view the exact name of the operating system, use one of the following methods:

      • Refer to the Auto registry key on the Windows virtual machine. The OSName string displays the exact name of the operating system on the virtual machine. Location of the registry key:

      Windows_virtual_machine\HKEY_LOCAL_MACHINE\Software\Microsoft\Virtual Machine\Auto

      • View the Backup Job Summary report. If the virtual machine is powered on at the time of backup and integration services are installed on the virtual machine, this report displays the exact name of operating systems on each backed up virtual machine. For more information, see Report.

      Guest DNS Hostname

      Enter a pattern to identify a hostname ora  domain.

      For example, to identify a specific host, enter myhost.mycompany.com,or to identify all hosts on that domain, enter *mycompany.com.

      Power State

      Select the power-on status of the virtual machines to be included in the subclient content. You can select from one of the following options:

      • Powered On - Identify VMs that are powered on.
      • Powered Off - Identify VMs that are powered off.
      • Other - Identify VMs with a different power-on status, such as Pause or Saved.


      Enter a pattern to identify virtual machines based on notes text contained in the Hyper-V Manager settings for the VM. For example, to identify VMs with a notes description that begins with "Test", enter Test*.

  5. To define multiple rules in a rule group, click + and define another rule.

    Note: The following options are available for a rule group with multiple rules:

    • If you define multiple rules in a rule group, you can indicate whether virtual machines are selected when they match all the rules (default), or when they match any of the rules.
    • To exclude virtual machines based on any of the criteria, use the Does Not Equal operator.  You can use this operator only when you are defining more than one rule.

      For rule groups with a single rule, the only operator you can use is Equals.

  6. Click OK.

What To Do Next

Back Up the Virtual Machines

Last modified: 4/15/2021 3:07:36 PM