Configuring Replication

Configure replication on the subclient for virtual machines to be replicated. Replication can be used to replicate virtual machines from a streaming backup, auxiliary copy, or backup copy.

If a virtual machine in a replication schedule is protected by multiple subclients, the VM will be replicated from the subclient with the latest backup.

The best method for scheduling backups of source VMs is to use the “Incremental Forever” approach:

  • Perform an initial full or synthetic full backup to create destination VMs using replication.
  • After the destination VM is created, run regular incremental backups to keep the destination VM current.
  • Run a synthetic full backup on a periodic basis to consolidate incremental backups into full VM backups without the need to touch production VMs. Synthetic full backups trigger a replication operation but only apply changes from any incremental backups that have not yet been replicated.

Note: Do not schedule full backups; a full backup results in recreating the destination VM completely.

Before You Begin

  • To add virtual machines to the replication schedule, the virtual machines must have been backed up at least once.
  • For Red Hat Linux VMs, add required Hyper-V drivers to the VMs before backing up the VMs and replicating the VMs. For more information, see Linux VMs do not boot or are unreachable after replication to Azure.
  • An Azure Stack Hub virtualization client is required to support the conversion of virtual machines to Azure Stack Hub. For more information, see Creating a Microsoft Azure Stack Hub Client.
  • To enable multiple jobs to run for each replication schedule, create the maxJobsPerSyncSchedule additional setting for CommServeDB.GxGlobalParam. When the value for this setting is greater than 1, multiple replication jobs execute simultaneously for each schedule, with each job using a separate stream. This setting enables schedules with large numbers of virtual machines to complete more quickly.


  1. From the CommCell Console, navigate to Client Computers > virtualization_client > Virtual Server > instance > backup_set.
  2. Right-click the subclient that contains the virtual machine data, and then select Live Sync > Configuration.
  3. From the Live Sync Options dialog box (General tab), click Add VMs.

    VMs that are already selected for the same schedule are grayed out.

  4. In the Select VMs for Live Sync dialog box, select the virtual machines that have been backed up, and then click OK.
  5. In the Live Sync Options dialog box define the following:
    • Azure Subscription: Displays the virtualization client for the Azure Stack Hub subscription. Select the Azure Stack Hub subscription client for the restore operation.
    • Proxy Client: Displays the proxies that have been selected for the virtualization client.
    • Add VMs: Click to browse for backed up virtual machines that can be replicated.
    • Remove VMs: Click to remove selected VMs from the replication schedule.
    • VM and Disk: This column displays the list of all the virtual machines and disks selected for replication (the source). Expand each virtual machine to view the disks in that virtual machine.
    • Change VM display name to (Destination VM): This column displays the existing name of each destination virtual machine. To change the name of any virtual machine, click in the corresponding row and enter the new name. If the VM display name of the source VM is retained for the replicated VM, select a different destination from the Client list.

      If the destination VM name matches the name of an existing virtual machine in the target location, the destination VM is not replaced unless a) it was created in a previous replication operation or b) you use the Unconditionally overwrite VM with the same name option.

    • Storage Account: Select the storage account to be used for all selected virtual machines or disk.

      You can specify any storage account within the selected region.

    • Settings: Click Configure to display the Azure Virtual Machine Configuration dialog box.
      • Destination VM: Displays the name of the destination VM.
      • Storage Account: Select the storage account to be used for all selected virtual machines or disk.
      • VM size: Select a VM size from the list. The VM sizes in the list are those that are available for the resource group or cloud service you selected.
      • Azure Virtual Network Options:

        Create Public IP: Select to create a public IP.

        Network Interface: Select one of the available network interfaces for the resource group from the list. If no VNet is selected, then the first VNet in the list and the first (default) subnet that it expands to will be attached to the synced VM.

        Note: Static IP addresses from a source VM are not replicated to the destination VM.

        Network Security Group (Azure Resource Manger): Select a security group for the destination VMs.

      • Click OK to save the values for the Azure Virtual Machine Configuration dialog box.
    • Unconditionally overwrite VM with the same name: Replace an existing virtual machine with the same name in the target location. If the destination VM is currently powered on, the replication fails, regardless of the setting for this option.
    • Distribute VM workload: To submit separate jobs for a replication schedule, select this option and select the number of VMs per job. When this option is used, jobs are submitted sequentially, with each job beginning after the previous job has completed.
  6. To replicate changes from an auxiliary copy or backup copy:
    1. Click Advanced
    2. In the Advanced Live Sync Options dialog box, click the Copy Precedence tab.
    3. Select Restore from copy precedence and enter the number of the storage copy properties for the auxiliary copy or backup copy.

    When replication is configured to use an auxiliary copy or backup copy, the replication operation uses the copy as the source rather than the primary backup. If the After Backup Job Completes option is selected in the schedule, replication automatically waits until the data is ready on the secondary copy before running the replication job.

  7. Click the Job Initiation tab.
  8. Select Schedule to create a schedule for replication.
  9. On the Schedule Details dialog, enter a schedule name, and then select one of the following options:
    • After Backup Job Completes: Automatically copy changes to the destination VM after each backup job.
    • If the schedule is configured to sync from a secondary copy, replication automatically waits until the data is ready on the secondary copy before running the replication job.
    • To replicate changes on a periodic basis, select Daily, Weekly, Monthly, or Yearly; then set up the replication schedule to control how often changes are replicated to the destination VM. If no new backups have been run since the last replication, the scheduled replication does not run.


For replication jobs, the Job Controller tab shows the Operation Type value as Replication. Separate replication jobs run for virtual machines in different subclients.

For destination virtual machines created by replication, any changes on the destination virtual machine are discarded, and the latest changes from the source VM are applied so that the source and destination machines remain in sync.

If the destination virtual machine is powered on, the replication job fails.

If a replication operation cannot be completed successfully after three attempts, the job fails. Live Sync jobs can be retried three times. After three failures for a virtual machine, replication is disabled for that virtual machine.

After each successful replication for a virtual machine, replication creates a snapshot for the VM that can be used with validation. An integrity snapshot will be created after every replication job on the destination VM to use it for validation in the next Incremental replication job.

In the Job Details dialog box (available from the Job Controller or restore history), the Virtual Machine Status tab provides status information for VMs. Double-click the row for a VM to view the following information for that virtual machine:

Source VM

The name of the source virtual machine.

Destination VM

The name of the destination virtual machine.

Resource Group/Cloud Services

The name for the machine where the destination virtual machine resides.


The job status of the replication operation for the VM (such as Completed, Waiting, Pending, or Failed).

Failure Reason

For failed replication operations, a brief description of the reason for the failure.


The name of the agent that performed the replication operation.

Restored Size

The size of the destination VM.

Sync Status

The replication status for the destination virtual machine.

Last Synced Backup Job

The job ID for the last backup job that was applied to the destination VM.

Last modified: 3/1/2021 8:01:30 PM