kolla-ansible/doc/source/reference/shared-services/glance-guide.rst

Glance - Image service

Glance backends

Overview

Glance can be deployed using Kolla and supports the following backends:

• file
• ceph
• vmware
• swift

File backend

When using the file backend, images will be stored locally under the value of the glance_file_datadir_volume variable, which defaults to a docker volume called glance. By default when using file backend only one glance-api container can be running.

For better reliability and performance, glance_file_datadir_volume should be mounted under a shared filesystem such as NFS.

Usage of glance file backend under shared filesystem:

glance_backend_file: "yes"
glance_file_datadir_volume: "/path/to/shared/storage/"

Ceph backend

To make use of ceph backend in glance, simply enable external ceph. By default will enable backend ceph automatically. Please refer to ../storage/external-ceph-guide on how to configure this backend.

To enable the ceph backend manually:

glance_backend_ceph: "yes"

VMware backend

To make use of VMware datastores as a glance backend, enable glance_backend_vmware and refer to ../compute/vmware-guide for further VMware configuration.

To enable the vmware backend manually:

glance_backend_vmware: "yes"

Swift backend

To store glance images in a swift cluster, the swift backend should be enabled. Refer to ../storage/swift-guide on how to configure swift in kolla. If ceph is enabled, will have higher precedence over swift as glance backend.

To enable the swift backend manually:

glance_backend_swift: "yes"

Upgrading glance

Overview

Glance can be upgraded with the following methods:

• Rolling upgrade
• Legacy upgrade

Rolling upgrade

As of the Rocky release, glance can be upgraded in a rolling upgrade mode. This mode will reduce the API downtime during upgrade to a minimum of a container restart, aiming for zero downtime in future releases.

By default it is disabled, so if you want to upgrade using this mode it will need to be enabled.

glance_enable_rolling_upgrade: "yes"

Warning

When using glance backend file without a shared filesystem, this method cannot be used or will end up with a corrupt state of glance services. Reasoning behind is because glance api is only running in one host, blocking the orchestration of a rolling upgrade.

Legacy upgrade

This upgrade method will stop APIs during database schema migrations, and container restarts.

It is the default mode, ensure rolling upgrade method is not enabled.

glance_enable_rolling_upgrade: "no"

Other configuration

Glance cache

Glance cache is disabled by default, it can be enabled by:

enable_glance_image_cache: "yes"
glance_cache_max_size: "10737418240" # 10GB by default

Warning

When using the ceph backend, is recommended to not use glance cache, since nova already has a cached version of the image, and the image is directly copied from ceph instead of glance api hosts. Enabling glance cache will lead to unnecessary storage consumption.

Glance caches are not cleaned up automatically, the glance team recommends to use a cron service to regularly clean cached images. In the future kolla will deploy a cron container to manage such clean ups. Please refer to Glance image cache <admin/cache.html>.