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Potential VM protection name confusion

Potential VM protection name confusion

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Lets say you create virtual machine protection and current conditions allow “Backup Using Child Partition Snapshot\<VM>” or in short; ‘online’ protection. Then you change the VM configuration and introduce one of the conditions that prohibit online protection (see below and  http://technet.microsoft.com/en-us/library/ff399205.aspx).  At this point online  protection (as the data source name suggests) will no longer happen. Instead ‘Backup Using Saved State\<VM>’ or ‘offline’ protection will occur but is not reflected in the data source name. Let’s repeat this; if a VM configuration condition changes after protection was created, the data source name which is indicative for the type of protection may no longer reflect the actual type of protection! Online protection could become offline and vice-versa.

DPM does not depend on data source names (but your scripts could) and does not change these once protection is created. Therefore it is recommendable to fully configure a VM with the intended most usual set of conditions before creating protection for it.

Let’s top-off repeating some details;

  • Backup Using  Child Partition Snapshot\<VM>” means ‘online’ protection.
    This is ‘full fidelity’ VSS protection; the VM is not paused and Hyper-V integration involves all VSS components to create a consistent backup,on the Hyper-V host (VHD’s) as well as all inside the guest.
  • Backup Using Saved State\<VM>” means ‘offline’ protection sometimes referred to as “Backup using Parent Partition
    This pauses the VM for the time required to take a shadow copy of volumes containing VHD’s that belong to this VM and does not involve VSS components inside the guest  (even if possible).
  • Nothing in this blog relates to using a hardware VSS provider or not!

Online protection is not possible when;

  • Backup (Volume Snapshot) Integration Service is not installed or disabled.
  • VM has one or more dynamic disks.
  • VM has one or more non-NTFS based volumes.
  • The VM Cluster Resource Group in a cluster setup is offline.
  • VM is not in a running state.
  • Shadow storage assignment of a volume inside the VM is explicitly set to a different volume other than itself.
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  • Nice heads up. Spent a few days figuring that out myself recently.

    Surely this behaviour (specifically DPM not updating data source names after they are created) is an issue to be addressed, and not by design?

    Cheers,

    Matt