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Cluster Shared Volumes Support for Hyper-V

Applies To: Windows Server 2008 R2

Cluster Shared Volumes, a feature available with some versions of failover clustering, simplifies the configuration and management of clustered virtual machines. With Cluster Shared Volumes, multiple clustered virtual machines can use the same LUN (disk) while still being able to fail over (or move from node to node) independently of one another.


In Windows Server® 2008 R2, the Cluster Shared Volumes feature included in failover clustering is only supported for use with the Hyper-V server role. The creation, reproduction, and storage of files on Cluster Shared Volumes that were not created for the Hyper-V role, including any user or application data stored under the ClusterStorage folder of the system drive on every node, are not supported and may result in unpredictable behavior, including data corruption or data loss on these shared volumes. Only files that are created for the Hyper-V role can be stored on Cluster Shared Volumes. An example of a file type that is created for the Hyper-V role is a Virtual Hard Disk (VHD) file.
Before installing any software utility that might access files stored on Cluster Shared Volumes (for example, an antivirus or backup solution), review the documentation or check with the vendor to verify that the application or utility is compatible with Cluster Shared Volumes.

This topic provides an overview and describes the paths and filenames associated with Cluster Shared Volumes. For more detailed information, see the topics listed in Additional references later in this topic.

In this topic

Overview of Cluster Shared Volumes

Paths associated with Cluster Shared Volumes

Filename extensions associated with Cluster Shared Volumes

Additional references

Overview of Cluster Shared Volumes

Cluster Shared Volumes is available in versions of Windows Server® 2008 R2 and of Microsoft® Hyper-V™ Server 2008 R2 that include the Failover Clustering feature. Volumes that are configured as Cluster Shared Volumes can be accessed by all nodes of a failover cluster. Each node can open and manage files on the volumes. Therefore, different nodes can host different virtual machines that all have files on the same volume. This design has many advantages, including the following:

  • Easier storage management: When virtual machines share volumes, fewer LUNs need to be configured and managed to host the same number of virtual machines.

  • Independent failover of virtual machines: Although multiple virtual machines are sharing the same volume, each virtual machine can fail over, or be moved or migrated, independently of other virtual machines.

  • No drive letter restrictions: Cluster Shared Volumes do not need to be assigned a drive letter, so you are not restricted by the number of available drive letters, and you do not have to manage volumes using GUIDs.

  • Enhanced availability: The Cluster Shared Volumes feature is designed to detect and handle many problems that would otherwise cause the storage to be unavailable to virtual machines. This includes detecting and handling storage connection problems (Cluster Shared Volumes reroutes the storage access through another node).

  • Efficient use of storage: You can make better use of disk space, because you do not need to place each Virtual Hard Disk (VHD) file on a separate disk with extra free space set aside just for that VHD file. Instead, the free space on a Cluster Shared Volume can be used by any VHD file on that LUN. This reduces the total amount of space that must be set aside for expansion, and simplifies capacity planning.

Paths associated with Cluster Shared Volumes

On a failover cluster that uses Cluster Shared Volumes, the files used for clustered virtual machines are stored and accessed by Hyper-V using the \ClusterStorage path on the system drive. For example, on a node that runs the operating system from the C drive, the path would be as follows:


The failover cluster provides a unique folder name for each volume under this path. An example is as follows:


The volume folder name can be renamed, but the ClusterStorage folder cannot be renamed. An example of a path with a volume folder with a changed name is as follows:


Filename extensions associated with Cluster Shared Volumes

Hyper-V uses files with the following filename extensions:

  • .vhd

  • .avhd

  • .vsv

  • .xml

  • .bin

  • .iso

  • .vfd

  • .exp

Cluster Shared Volumes should not be used to store files for any applications, features, or roles other than Hyper-V. Only Hyper-V is supported to use these files. Using these files from other applications, features, or roles is not supported.

Additional references