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      Copyright (c) 2013 OpenStack Foundation
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      Licensed under the Apache License, Version 2.0 (the "License"); you may
      not use this file except in compliance with the License. You may obtain
      a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0

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      WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
      License for the specific language governing permissions and limitations
      under the License.

Drivers
=======

Cinder exposes an API to users to interact with different storage backend
solutions. The following are standards across all drivers for Cinder services
to properly interact with a driver.

Minimum Features
----------------

Minimum features are enforced to avoid having a grid of what features are
supported by which drivers and which releases. Cinder Core requires that all
drivers implement the following minimum features.

Havana
------

* Volume Create/Delete
* Volume Attach/Detach
* Snapshot Create/Delete
* Create Volume from Snapshot
* Get Volume Stats
* Copy Image to Volume
* Copy Volume to Image
* Clone Volume

Icehouse
--------

* All of the above plus
* Extend Volume

Volume Stats
------------

Volume stats are used by the different schedulers for the drivers to provide
a report on their current state of the backend. The following should be
provided by a driver.

* driver_version
* free_capacity_gb
* reserved_percentage
* storage_protocol
* total_capacity_gb
* vendor_name
* volume_backend_name

**NOTE:** If the driver is unable to provide a value for free_capacity_gb or
total_capacity_gb, keywords can be provided instead. Please use 'unknown' if
the array cannot report the value or 'infinite' if the array has no upper
limit.