The Image Service includes the following components: glance-api. Accepts Image API calls for image discovery, retrieval, and storage. glance-registry. Stores, processes, and retrieves metadata about images. Metadata includes items such as size and type. The registry is a private internal service meant only for use by the Image Service itself. Do not expose it to users. Database. Stores image metadata. You can choose your database depending on your preference. Most deployments use MySQL or SQlite. Storage repository for image files. The Image Service supports a variety of repositories including normal file systems, Object Storage, RADOS block devices, HTTP, and Amazon S3. Some types of repositories support only read-only usage. A number of periodic processes run on the Image Service to support caching. Replication services ensures consistency and availability through the cluster. Other periodic processes include auditors, updaters, and reapers. As shown in , the Image Service is central to the overall IaaS picture. It accepts API requests for images or image metadata from end users or Compute components and can store its disk files in the Object Storage Service.