OpenStack Block Storage can quickly create a volume from an image
that refers to a volume storing image data (Image-Volume). Compared to
the other stores such as file and swift, creating a volume from a
Volume-backed image performs better when the block storage driver
supports efficient volume cloning.

If the image is set to public in the Image service, the volume data
can be shared among projects.

Configure the Volume-backed
image

Volume-backed image feature requires locations information from the
cinder store of the Image service. To enable the Image service to use
the cinder store, add cinder to the stores
option in the glance_store section of the
glance-api.conf file:

stores = file, http, swift, cinder

To expose locations information, set the following options in the
DEFAULT section of the glance-api.conf
file:

show_multiple_locations = True

To enable the Block Storage services to create a new volume by
cloning Image-Volume, set the following options in the
DEFAULT section of the cinder.conf file. For
example:

allowed_direct_url_schemes = cinder

To enable the openstack image create --volume <volume>
command to create an image that refers an Image-Volume, set
the following options in each back-end section of the
cinder.conf file:

image_upload_use_cinder_backend = True

By default, the openstack image create --volume <volume>
command creates the Image-Volume in the current project. To store the
Image-Volume into the internal project, set the following options in
each back-end section of the cinder.conf file:

image_upload_use_internal_tenant = True

To make the Image-Volume in the internal project accessible from the
Image service, set the following options in the
glance_store section of the glance-api.conf
file:

• cinder_store_auth_address
• cinder_store_user_name
• cinder_store_password
• cinder_store_project_name

Creating a Volume-backed
image

To register an existing volume as a new Volume-backed image, use the
following commands:

$ openstack image create --disk-format raw --container-format bare IMAGE_NAME

$ glance location-add <image-uuid> --url cinder://<volume-uuid>

If the image_upload_use_cinder_backend option is
enabled, the following command creates a new Image-Volume by cloning the
specified volume and then registers its location to a new image. The
disk format and the container format must be raw and bare (default).
Otherwise, the image is uploaded to the default store of the Image
service.

$ openstack image create --volume SOURCE_VOLUME IMAGE_NAME