HV 2012 R2 VM backup with Veeam RRS feed

  • Question

  • Hi

    We are trying to understand the Veeam backup with HV 2012 R2 VMs, below are the steps mentioned with Veeam documentation

    1. Veeam Backup & Replication interacts with the Microsoft Hyper-V host VSS Service and requests backup of a specific VM.
    2. The Microsoft VSS Writer on the Microsoft Hyper-V host passes the request to the Microsoft Hyper-V Integration Components (HV-IC) installed inside the VM guest OS.
    3. The HV-IC acts as a VSS Requestor for the framework inside the VM. It communicates with this framework and requests backup of Microsoft VSS-aware applications running on the VM.
    4. VSS Writers for Microsoft VSS-aware applications on the VM are instructed to quiesce application data.
    5. After the applications are quiesced, Microsoft Hyper-V VSS takes a backup checkpoint of the VM. Every virtual disk of a VM receives a temporary file named GUID.avhdx. All new writes that occur to the VM until the volume snapshot is taken are redirected to this file
    6. Right after taking the backup checkpoint, Microsoft Hyper-V VSS takes another auxiliary checkpoint — auto-recovery checkpoint. Every virtual disk of a VM receives a temporary file named GUID-Autorecovery.avhdx. The auto-recovery checkpoint helps make sure that VM data is consistent during backup. The auto-recovery checkpoint does not depend on the backup checkpoint — it is taken independently in a new checkpoint chain.
    7. The framework inside the VM takes an internal snapshot using a Microsoft Hyper-V Integration Services Shadow Copy provider in the VM guest OS.
    8. The created internal snapshot is passed to the HV-IC.
    9. The HV-IC notifies the hypervisor that the VM is ready for backup.
    10. Microsoft Hyper-V VSS performs auto-recovery — it mounts the auto-recovery checkpoint to the VM, rolls back data on the VM to the consistent state.
    11. The Microsoft Hyper-V host VSS provider takes a snapshot of a volume on which VM disks are located (external snapshot).
    12. The auto-recovery checkpoint is merged with the original VM.
    13. The volume snapshot is presented to VBR. Veeam Backup & Replication reads VM data from the volume snapshot in one of two backup modes — on-host backup or off-host backup.
    14. After the backup is complete, the volume snapshot is deleted, and the backup checkpoint is merged with the original VM

    Here during the process it creates 2 checkpoints (step 5: backup checkpoint & all new writes redirected to this checkpoint, step 6: independent checkpoint auto-recovery checkpoint). Then once after created both the checkpoints VM takes internal snapshot. Then in step 10, it mounts auto-recovery checkpoint to complete the auto recovery process. Auto recovery process is as follows:- Microsoft Hyper-V host VSS Writer rolls back a VM on the external snapshot to the state of the internal snapshot. All changes that took place after the internal snapshot was taken are discarded. This way, VM data inside the external snapshot is brought to a completely consistent state. 

    Here we took internal VM snapshot after taking both the checkpoints, so our concern is how auto-recovery process happens by mounting auto-recovery checkpoint?

    Hope someone can clarify it....


    Tuesday, May 22, 2018 8:40 AM

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