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Backups (Microsoft Hyper-V)

The Virtual Server Agent on the Hyper-V hosts can back up the virtual machines on the Hyper-V Server or Hyper cluster depending on the configuration settings on the virtualization client, backup set, and subclient components.

When a virtual machine is discovered during backup, a client for the VM is created in the CommCell Console if one does not already exist. If a virtual machine with spaces or special characters in its name is discovered during backup, the spaces or special characters are replaced with underscores ('_') when creating the VM client name that is displayed in the CommCell Console. The VM name with spaces or special characters is still displayed on the Virtual Machine Status tab for the backup job, in the backup job summary, and in reports that include the VM name. The following special characters are replaced:

[ \ \ | ` ~ ! @ # $ % ^ & * + = < > ? , { } ( ) : ; ' \ " \ \ s / ]

What Gets Backed Up

  • Virtual machines
  • VHD and VHDX files
  • Snapshot files
  • Configuration files for the virtual machines
  • Metadata required for granular recovery of files (NTFS and ext3 volumes only)
  • VHDX formatted hard disks with sector size of 4K bytes without metadata

What Does Not Get Backed Up

  • Pass-through disks
  • Windows Storage Spaces
  • Hard links (only for disk-level backup)
  • Virtual machine smart paging files
  • Certain virtual machines in which Volume Shadow Copy Service (VSS) fails to create a shadow
  • Devices residing in a guest virtual machine over iSCSI or vHBA

Shared VHDX Files

  • Backups of shared VHDX files are only supported for streaming backups, and are not supported for SnapProtect backups.
  • To back up shared VHDX files, on the Backup Options tab of the subclient properties, select the Perform application consistent backup option before performing a backup for the subclient. Although you must specify the application consistent backup option, shared VHDX disk files can only be backed up in a crash consistent format (a Microsoft limitation).
  • When you restore a VM that includes a shared VHDX disk file, only the ACLs for the restored VM are restored, not the ACLs for other VMs that refer to the disk. After the restore, you might need to reset the ACLs and modify the security properties for the disk to include all VMs that shared the disk.
  • If multiple VMs that refer to a shared VHDX are restored, each gets its own copy of the disk.

Backup Types

You can perform the following types of backups, either immediately or on a schedule:

  • Full backups: Back up the entire virtual machine. This is the most comprehensive backup.
  • Incremental backups: Back up virtual machine data that has changed since the most recent backup.
  • Differential backups: Back up virtual machine data that has changed since the most recent full backup.
  • Synthetic Full backups: Consolidate virtual machine data from the most recent full backup with subsequent incremental and differential backups.

Backup Job Management

  • If some parts of a virtual machine backup job are not completed successfully, the job status is "Completed w/ one or more errors." You can view the Job Details dialog box and select the Virtual Machine Status tab to check the status of specific VMs.
  • If the status for a specific virtual machine is "Partial Success," some information for the VM was successfully backed up, but other information was not. Failed items for a VM contribute to the Failed Objects count in the Backup Job Summary Report.
  • A VM is only included in a backup of failed VMs if the VM is marked as Failed in the Virtual Machine Status tab. VMs that complete with partial success are not included as failed VMs.

Controlling Metadata Collection and Granular Recovery

By default, file and folder metadata is collected during backups. Metadata collection is required for recovery of guest files and folders from virtual machines.

If you do not need to recover file and folder information for some virtual machines, you can configure backups to disable the granular recovery option.