openstack/openstack-manuals
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openstack-manuals/doc/admin-guide-cloud/source/blockstorage_volume_backed_image.rst
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Volume-backed image

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 tenants.

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:

glance_api_version = 2
allowed_direct_url_schemes = cinder

To enable the cinder upload-to-image 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 upload-to-image command creates the Image-Volume in the current tenant. To store the Image-Volume into the internal tenant, set the following options in each back-end section of the cinder.conf file:

image_upload_use_internal_tenant = True

Creating a Volume-backed image

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

$ glance image-create --disk-format raw --container-format bare --name <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.

$ cinder upload-to-image <volume> <image-name>

Note

Currently, the cinder store of the Image services does not support uploading and downloading of image data. By this limitation, Volume-backed images can only be used to create a new volume.