Add Quobyte cinder backend spec

Partially-Implements: blueprint cinder-quobyte-backend

Change-Id: I6de535ea4081fe0de52858ae582420617204e914

specs/quobyte-cinder.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
+
+======================================
+Add support for Quobyte cinder backend
+======================================
+
+https://blueprints.launchpad.net/kolla-ansible/+spec/cinder-quobyte-backend
+
+Currently there is no option to enable the use of Quobyte as a backend for Cinder
+within kolla. Since there is support for Quobyte in Cinder and Nova, it should be
+a valid option in Kolla as well.
+
+Problem description
+===================
+
+Quobyte is a software defined storage solution that has a Cinder driver allowing
+it to be used with Cinder and Nova. Currently there is no option in Kolla to
+enable the use of Quobyte in Cinder and Nova.
+
+Use cases
+---------
+Allowing the use of a Quobyte volume as a backend for Cinder in Kolla.
+
+Proposed change
+===============
+
+- Add an ``enable_cinder_backend_quobyte`` option to ``etc/kolla/globals.yml``
+- If enabled, add the shared propagation to the ``/var/lib/nova/mnt`` bind, same as NFS.
+  This would require extending the logic in ``ansible/roles/nova/defaults/main.yml`` to
+  check if either NFS or Quobyte are enabled as Cinder backends.
+- Update documentation in ``doc/source/reference/cinder-guide.rst`` to include configuration
+  of the Quobyte Cinder driver.
+
+Security impact
+---------------
+None
+
+Performance Impact
+------------------
+None
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Patrick O'Neill <patrick.oneill@vscaler.com>
+
+Milestones
+----------
+
+Target Milestone for completion:
+  stein-1
+
+Work Items
+----------
+
+1. Create variable in globals.yml to allow Cinder Quobyte backend to be enabled.
+2. Define Quobyte as a valid backend option in prechecks task.
+3. Add shared propagation to docker bind mounts in Nova.
+4. Update documentation to cover Cinder and Nova driver configuration for Quobyte.
+
+Testing
+=======
+Following the cinder reference of kolla to use quobyte as cinder backend. Perform
+checks to ensure that the backend is functional by creating volumes in cinder
+and mounting volumes to instances.
+
+Documentation Impact
+====================
+``doc/source/reference/cinder-guide.rst`` needs to be updated to include a section
+on Quobyte driver configuration.