Merge "Support volume backup of qcow2 format volume"

specs/juno/support-volume-backup-for-qcow2.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 volume backup for qcow2
+================================
+
+https://blueprints.launchpad.net/cinder/+spec/support-volume-backup-for-qcow2
+
+Currently, cinder-backup doesn't support qcow2 format disk. Add the support
+for it will make drivers which use qcow2 as volume, such as glusterfs etc,
+work together with cinder-backup, and can also make nfs driver use qcow2 as
+volume be possible.
+
+Problem description
+===================
+
+Currently, cinder-backup doesn't support qcow2 format disk because the backup
+code assumes the source volume is a raw volume. The destination (i.e. swift,
+rbd) should absolutely remain universal across all volume back-ends.
+
+Proposed change
+===============
+
+* Add qemu-nbd support to cinder-backup. Qemu-nbd can mount qcow2 volume as
+  a raw device to the host
+* The backup_volume method in base class of remotefs driver (cinder.volume.
+  drivers.nfs.RemoteFsDriver:backup_volume) will mount qcow2 volume as nbd
+  device before call backup_service's backup method
+
+Alternatives
+------------
+
+None
+
+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
+---------------------
+
+Storage node which running cinder-volume will contains nbd kernel module.
+
+Developer impact
+----------------
+
+None
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  Trump.Zhang <zhangleiqiang@huawei.com>
+
+Work Items
+----------
+
+* Add qemu-nbd support to cinder-backup. Qemu-nbd can mount qcow2 volume as
+  a raw device to the host
+* The backup_volume method in base class of remotefs driver (cinder.volume.
+  drivers.nfs.RemoteFsDriver:backup_volume) will mount qcow2 volume as nbd
+  device before call backup_service's backup method
+
+
+Dependencies
+============
+
+None
+
+
+Testing
+=======
+
+None
+
+
+Documentation Impact
+====================
+
+None
+
+
+References
+==========
+
+None