Working with shared volumes

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PowerVC allows applications to have shared access to a volume. This allows advanced applications that can manage multiple connections to the volume to use PowerVC more effectively. A volume must be attached to multiple virtual machines for the application to have shared access to the volume.

A volume can be attached to as many virtual machines as the backing storage supports. PowerVC does not limit the number of virtual machines that can share access to the volume.
Note: Shared volumes are not supported on IBM® i.

Considerations

Be aware of the following considerations when setting up shared volumes:
  • The backing storage must support shared volume access.
  • If the application requires the volumes to be attached in a specific order, then the administrator must attach the volumes in that order.

    The order in which the volumes are discovered within the virtual machines might or might not be the same as the attachment order. The order in which the volumes are discovered on the operating system depends on the operating system and the multi-pathing solution implemented by the virtual machine. Applications must use the same volume across all the virtual machines to which the volume is attached.

  • When you manage an existing virtual machine that has a volume that is attached to multiple virtual machines, PowerVC marks that volume as eligible for shared access.
  • To prevent a volume from being attached to multiple virtual machines, deselect Enable sharing on the volume's properties page in the PowerVC user interface.
  • The application is responsible for determining how to use each volume and providing access control. Some applications require concurrent access and some require failover access. PowerVC does not control volume access. The administrator might need to configure SCSI reserves appropriately within the virtual machine to accommodate the type of shared access needed by the application.
  • Do not attach a volume to more than one virtual machine if the application using that volume is not designed for shared access.
  • You cannot delete a volume that is shared with a virtual machine that is not managed by PowerVC. If you try to delete the volume, you will receive an error stating that the volume is in use and cannot be deleted.
  • If a volume is attached to multiple virtual machines, it must have the same connectivity type on all of them. Therefore, you cannot change the Boot Set attribute for a volume that is attached to another virtual machine.