dd1671a7bb
Updates: - Removed references to the S3 backend, whose driver was removed with change I032b0fc16400cbd2112687d38e010128be699221 - Clarified use of filesystem store, based on an actual question asked in #openstack-glance - Expanded the list of backends mentioned where appropriate Change-Id: Ic0220a714beadd54cdf0c86ce65ab9223a88a3de
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Image service overview
The OpenStack Image service is central to Infrastructure-as-a-Service
(IaaS) as shown in get_started_conceptual_architecture. It accepts API
requests for disk or server images, and metadata definitions from end
users or OpenStack Compute components. It also supports the storage of
disk or server images on various repository types, including OpenStack
Object Storage.
A number of periodic processes run on the OpenStack Image service to support caching. Replication services ensure consistency and availability through the cluster. Other periodic processes include auditors, updaters, and reapers.
The OpenStack Image service includes the following components:
- glance-api
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Accepts Image API calls for image discovery, retrieval, and storage.
- glance-registry
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Stores, processes, and retrieves metadata about images. Metadata includes items such as size and type.
Warning
The registry is a private internal service meant for use by OpenStack Image service. Do not expose this service to users.
- Database
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Stores image metadata and you can choose your database depending on your preference. Most deployments use MySQL or SQLite.
- Storage repository for image files
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Various repository types are supported including normal file systems (or any filesystem mounted on the glance-api controller node), Object Storage, RADOS block devices, VMware datastore, and HTTP. Note that some repositories will only support read-only usage.
- Metadata definition service
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A common API for vendors, admins, services, and users to meaningfully define their own custom metadata. This metadata can be used on different types of resources like images, artifacts, volumes, flavors, and aggregates. A definition includes the new property's key, description, constraints, and the resource types which it can be associated with.