The consistency of virtual machine backups differs based on the consistency level chosen in the policy. Before the block-based backup is performed Protector will create a checkpoint for every virtual machine.
Application consistent checkpoints will use Hyper-V integration services to quiesce the data inside the VM. In case of Windows VMs, Protector will utilize VSS within the virtual machine to save application and filesystem data to disk. For Linux, the Hyper-V integration will request a quiesce, however usually this will only cause the filesystem buffers to be saved to disk. If an application consistent VM checkpoint cannot be created, Protector will create a crash consistent checkpoint instead.
Crash consistent checkpoints will create a checkpoint of the virtual disks as they are.