Backup Hyper-V VMs on Cluster Shared Volumes (CSVs)

What are Cluster Shared Volumes (CSVs)?

Cluster Shared Volumes (CSVs) were introduced by Microsoft in Windows Server 2008 R2 and changed the way storage is provisioned in a Hyper-V cluster. Cluster Shared Volumes enable multiple Hyper-V hosts to read and write to the same storage at the same time. Furthermore, it allows multiple hosts to have ownership of multiple virtual machines that are running on the same Hyper-V backend storage. Cluster Shared Volumes also allow for much faster failover between Hyper-V hosts.

The Cluster Shared Volumes failover process does not require transferring ownership from one host to another, as well as the additional tasks of dismounting and remounting drives between them. As you might expect, CSVs make it much easier to configure Hyper-V storage for virtual machines across multiple Hyper-V hosts. Furthermore, the reduced complexity of managing Hyper-V storage reduces the total cost of ownership (TCO) for organizations that manage Hyper-V clusters.

Backup of VM’s on CSV using BDRSuite

BDRSuite uses the Microsoft VSS framework and Microsoft Hyper-V VSS components to backup VMs on local storage and CSV. BDRSuite communicates with the Microsoft VSS framework as a Microsoft VSS requestor. It obtains information from Microsoft VSS about available Microsoft VSS components, specifies which components Microsoft VSS must use, identifies volumes containing VM files, and instructs the Microsoft VSS coordinator to create volume snapshots.

Before creating a snapshot of a volume, all VMs on the volume must be idle: no incomplete transactions, open files, or so on. BDRSuite prepares Microsoft Hyper-V VMs for backup using the following methods, depending on the OS of the guest VMs

VMs with Windows Guest OS

BDRSuite employs the Child VM Snapshot method, a native Microsoft Hyper-V mechanism that enables you to create an application-consistent image of running VMs with no downtime.

VMs with Linux Guest OS

BDRSuite employs the Saved State method, a native Microsoft Hyper-V mechanism that usually requires some VM downtime. Microsoft Hyper-V places a VM in the save state to quiesce guest OS operations (hibernates it).

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