Support backup import on another Storage database

Currently a volume backup can only be restored on the same Block
Storage service. This is because restoring a volume from a backup
requires metadata available on the remote database.

This proposal is to store backup metadata together
with the data, so a user will be able to restore a volume backup
on another Block Storage.

Change-Id: Ibafe96a3d1dcee8b6f28dac2f18814d3b7fcd9ef
Implements: blueprint support-backup-import-on-another-storage-database

specs/newton/support-backup-import-on-another-storage-database.rst

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+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+====================================================================
+Support backup import on another Storage database
+====================================================================
+
+URL of launchpad blueprint:
+
+https://blueprints.launchpad.net/cinder/+spec/Support-backup-import-on-
+another-Storage-database
+
+* This backup service can use a backup extra metadata in order
+  to import a backup on a different Block Storage.
+
+Problem description
+===================
+
+* Currently a volume backup can only be restored on the same Block Storage
+  service.
+  This is because restoring a volume from a backup requires metadata available
+  on the database used by the Block Storage service.
+
+* In order to import backup metadata on another Block Storage database
+  (i.e disaster recovery site), one has to save the metadata of a volume
+  backup available on the source database, and then replicate it together
+  with the data to the other Block Storage site.
+
+* Combination of the local backup service that exports and stores
+  this metadata, together with replication to another Block Storage site,
+  allows you to completely restore the backup even in the event of
+  a catastrophic database failure.
+
+* In addition, having a backup metadata together with a volume backup,
+  also provides volume portability.
+  Specifically, backing up a volume and exporting its metadata will allow you
+  to restore the volume on a completely different Block Storage database,
+  or even on a different cloud service.
+
+Use Cases
+=========
+
+* When a user wants to save backup metadata together with volume backup for
+  volume portability purpose, or for replication purpose to disaster
+  recovery site, and be able to restore a volume from a backup on the other
+  Block Storage site.
+
+Proposed change
+===============
+
+* In order to support backup import on a different Block Storage database,
+  we need to extend chunked backup driver:
+
+  *  Enabling to save backup metadata together with the data.
+  *  Add a cinder client api command, that will parse backup metadata from
+     backup_metadata file, and import that metadata to the other
+     Block Storage database.
+  *  User will be able to restore a volume backup on the other
+     Block Storage, using cinder backup restore api.
+
+Alternatives
+------------
+
+Support only storage on local storage.
+Use slow manual backup and restore methods.
+
+Data model impact
+-----------------
+
+None.
+
+REST API impact
+---------------
+
+None.
+
+Security impact
+---------------
+
+None.
+
+Notifications impact
+--------------------
+
+None.
+
+Other end user impact
+---------------------
+
+None.
+
+Performance Impact
+------------------
+
+None.
+
+Other deployer impact
+---------------------
+
+None.
+
+Developer impact
+----------------
+
+None.
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  ronen-mesonzhnik
+
+Other contributors:
+  None
+
+Work Items
+----------
+
+- Implement get_extra_metadata that will return backup's corresponding
+  database information as encoded string metadata.
+- Implement a cinder client api command that can take a backup metadata
+  file, and do the import from it.
+
+Dependencies
+============
+
+None.
+
+Testing
+=======
+
+None.
+
+Documentation Impact
+====================
+
+* In addition to the existing command 'cinder backup-import <METADATA>',
+  there will be a command that can accept a file:
+  'backup-import-record-from-backup-metadata-file <file_path>'
+
+References
+==========
+
+* Link to Export and import backup metadata documentation:
+  http://docs.openstack.org/admin-guide-cloud/blockstorage_volume_backups_export_import.html