Notes on full virtual machine restore

Article:HOWTO44969  |  Created: 2011-03-16  |  Updated: 2011-03-16  |  Article URL http://www.symantec.com/docs/HOWTO44969
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Notes on full virtual machine restore

This topic pertains to NetBackup for Hyper-V.

Note the following:

  • A backup of the full virtual machine can be restored only to a Windows Server 2008 and later with the Hyper-V role enabled.

  • By default, the NetBackup client on the Hyper-V server does not have Windows Administrator privileges. You can restore a full virtual machine from the NetBackup server. You cannot restore a full virtual machine from a NetBackup client that does not have Administrator privileges.

  • For the virtual machines that are configured in a volume GUID with a differencing disk in another volume GUID, redirected restores are not supported.

    See Restored virtual machine fails to start.

  • When you restore the virtual machine to its original location with the Overwrite virtual machine option, note: The same virtual machine on the Hyper-V server is automatically turned off and deleted before the restore. The .vhd files of the virtual machine on the Hyper-V server are overwritten by the .vhd files from the backup image. If any new .vhd files were created after the backup, those files are not removed.

  • When you restore the virtual machine to a different location on the original Hyper-V server or to a different server, note: The same virtual machine (if it exists) on the Hyper-V server is automatically turned off and deleted before the restore if you choose the Overwrite virtual machine option. The .vhd files of the deleted virtual machine, however, are not deleted. You must delete those .vhd files.

  • When you restore the virtual machine to a Hyper-V server that has a virtual machine of the same GUID, you must select the Overwrite virtual machine option. Otherwise, the restore fails.

  • If you restore a virtual machine without the Overwrite virtual machine option, note: You must remove the current virtual machine and its .vhd files from the destination server before you start the restore. If you remove the virtual machine but leave one or more of its .vhd files on the destination server, the .vhd files from the backup are not restored.

  • (This item is a limitation in VSS and the Hyper-V writer, not in NetBackup.) If the virtual machine contains Hyper-V snapshot files (.avhd files), NetBackup cannot restore the virtual machine to a different location or to a different Hyper-V server.

    Note the following:

    • This issue has been fixed in Windows Server 2008 R2 (restore server).

    • This restriction does not apply in either of the following cases: When you restore the virtual machine to its original location on the original Hyper-V server, or when you restore to a staging location.

    Note that NetBackup does not create Hyper-V snapshot files (.avhd).

  • (This item is a limitation in VSS, not in NetBackup.) Immediately after a full virtual machine is restored, the virtual machine volume may be larger than it was when the virtual machine was backed up. The increase is normal: After the restore, snapshot-related cache files remain on the volume. After about 20 minutes, the cache files are automatically removed and the volume returns to its original size

    Note: A new backup of the restored virtual machine could fail if the virtual machine volume contains insufficient space to create a snapshot for the backup. According to Microsoft, this situation should not occur as long as the virtual machine volume has at least 10 to 15% free space.

  • If you attempt to do a full restore of two virtual machines at the same time, and the two virtual machines share a virtual hard disk (.vhd file) that both restore jobs have selected to restore, a race condition may result. The two jobs may simultaneously attempt to access the same .vhd file, but only one job gains access to the file. The other job is denied access, and that job may fail with error code 185.

    See NetBackup status codes related to Hyper-V.

  • If you restore a virtual machine to a different Hyper-V server, note: The original Hyper-V server and the target server must have the same number of network adapters (NICs). You must configure the network adapter(s) for the restored virtual machine on the target server.

    See Restored virtual machine fails to start.

  • Windows Hyper-V provides no mechanism for quiescing file system activity on Linux virtual machines. Therefore, at the time of backup, a snapshot of a Linux virtual machine may be in an inconsistent state (crash-consistent). Note that the backup succeeds. For restore of inconsistent Linux files from the backup, NetBackup creates a NetBackup.lost+found directory for each Linux volume.

    See About the NetBackup lost and found directory on Linux.

See About restoring individual files

See NetBackup administrator tasks for Hyper-V


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