The application-aware mode for Hyper-V uses the Volume Shadow Copy Service (VSS).
Hyper-V 2012 doesn't have an implementation of VSS, so when the Application-aware mode is enabled, the checkpoint works as follows:
- NAKIVO Backup & Replication injects a runtime VSS Driver into the VM.
- NAKIVO Backup & Replication requests the VSS Driver to create a quiesced checkpoint.
- VSS Driver uses VSS inside a Windows VM to freeze I/O requests of applications inside the OS.
- If OS quiescing fails to create an application-consistent checkpoint, NAKIVO Backup & Replication displays this error.