In order for the child VM snapshot method to be used when backing up a host server, the following 5 conditions must be met:
- Backup (volume snapshot) Integration Service is installed and running in the child VM. The service name is "Hyper-V Volume Shadow Copy Requestor". Windows 2000: Backup Integration Service is not supported.
- The child VM must be in the running state.
- The Snapshot File Location for the VM is set to be the same volume in the host operating system as the VHD files for the VM.
- All volumes in the child VM are basic disks and there are no dynamic disks.
- All disks in the child VM must use a file system that supports snapshots (for example, NTFS).
These conditions and more details about this process can be found in this Microsoft article - https://msdn.microsoft.com/en-us/library/dd405549%28v=vs.85%29.aspx.
Once the child VM snapshot method is able to be used, the VMs will no longer suspend and resume during a backup of the host.