In VMware Integrated OpenStack 6.0, you can create Cinder volumes as First Class Disks (FCDs) instead of VMDKs.

An FCD, also known as an Improved Virtual Disk (IVD) or Managed Virtual Disk, is a named virtual disk independent of a virtual machine. Using FCDs for Cinder volumes eliminates the need for shadow virtual machines.

The FCD back end is offered in addition to the default VMDK back end. If you select FCD as the back-end driver for Cinder, you can use both FCD and VMDK volumes in the same deployment. You can also attach FCD and VMDK volumes to the same OpenStack instance.

To specify the back-end driver used for volume creation, create volume types with the volume_backend_name extra spec set to the name of the desired driver. Then select the volume type when you create volumes.

Existing VMDK volumes cannot be automatically converted to FCD volumes. To manually convert a VMDK volume, detach the volume from all instances, unmanage it, and manage it again. For information, see Manage a Volume.

If you want to use FCD volumes with VMware Integrated OpenStack, be aware of the following:

  • vSphere 6.7 Update 2 or later is required to use FCD volumes.
  • vSphere 6.7 Update 3 or later is required to perform the following operations on volumes that are attached to powered-on instances:
    • Creating a volume from a snapshot
    • Backing up a volume snapshot using a temporary volume created from a snapshot
  • Storage DRS is not supported for FCD volumes.
  • Volume multi-attach is not supported for FCD volumes.
  • FCD volumes must be backed by a shared datastore.
  • FCD volumes that are in use cannot be cloned, retyped, or extended.
  • After you set a storage policy on an FCD volume, you cannot remove the storage policy from the volume. However, you can change the storage policy used by an unattached volume.
  • Instances that have an FCD volume attached cannot be migrated. You must detach the volume before migrating the instance.
  • FCD volumes with snapshots cannot be extended.