Image-Volume cache¶

Configure the Internal Tenant¶

The Image-Volume cache requires that the Internal Tenant be configured for the Block Storage services. This project will own the cached image-volumes so they can be managed like normal users including tools like volume quotas. This protects normal users from having to see the cached image-volumes, but does not make them globally hidden.

To enable the Block Storage services to have access to an Internal Tenant, set the following options in the cinder.conf file:

cinder_internal_tenant_project_id = PROJECT_ID
cinder_internal_tenant_user_id = USER_ID

An example cinder.conf configuration file:

cinder_internal_tenant_project_id = b7455b8974bb4064ad247c8f375eae6c
cinder_internal_tenant_user_id = f46924c112a14c80ab0a24a613d95eef

Configure the Image-Volume cache¶

To enable the Image-Volume cache, set the following configuration option in the cinder.conf file:

image_volume_cache_enabled = True

[ceph]
image_volume_cache_enabled = True

This can be scoped per back end definition or in the default options.

There are optional configuration settings that can limit the size of the cache. These can also be scoped per back end or in the default options in the cinder.conf file:

image_volume_cache_max_size_gb = SIZE_GB
image_volume_cache_max_count = MAX_COUNT

By default they will be set to 0, which means unlimited.

For example, a configuration which would limit the max size to 200 GB and 50 cache entries will be configured as:

image_volume_cache_max_size_gb = 200
image_volume_cache_max_count = 50

Notifications¶

Cache actions will trigger Telemetry messages. There are several that will be sent.

• image_volume_cache.miss - A volume is being created from an image which was not found in the cache. Typically this will mean a new cache entry would be created for it.

• image_volume_cache.hit - A volume is being created from an image which was found in the cache and the fast path can be taken.

• image_volume_cache.evict - A cached image-volume has been deleted from the cache.

Managing cached Image-Volumes¶

In normal usage there should be no need for manual intervention with the cache. The entries and their backing Image-Volumes are managed automatically.

If needed, you can delete these volumes manually to clear the cache. By using the standard volume deletion APIs, the Block Storage service will clean up correctly.