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 External Ceph
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 VMware - Nova Virtualisation Driver 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 Swift - Object storage service 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¶
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.
