glance-api service can be configured to cache images to local machine's disk. Once configured, the local cache automatically stores copies of images that are successfully retrieved and served. In this configuration,
glance-api can run on multiple hosts without retrieving the same image from remote storage multiple times, leading the OpenStack environment to handle better scalability. Using Glance image caching is transparent to the user and doesn't change any of Glance's operations. The user does not know of the images are served from the backend storage or from
glance-api caching mechanism.
Before enabling and configuring Glance image caching, make sure that glance is configured and can successfully serve images.