Add the StorPool volume attach/detach proposal.

Change-Id: I38960514e4cd914cb8acc3a2250c213b1d485e17

specs/kilo/approved/libvirt-storpool-volume-attach.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
+
+==========================================
+StorPool Volume Attachment
+==========================================
+
+https://blueprints.launchpad.net/nova/+spec/libvirt-storpool-volume-attach
+
+There are various Nova volume drivers providing access to Cinder volumes using
+specific types of storage, such as LVM, RBD, etc.  The purpose of this
+blueprint is to add a driver supporting the volumes defined in a StorPool
+cluster.
+
+Problem description
+===================
+
+StorPool is distributed data storage software running on standard x86 servers.
+StorPool aggregates the performance and capacity of all drives into a shared
+pool of storage distributed among the servers.  Within this storage pool the
+user creates thin-provisioned volumes that are exposed to the clients as block
+devices.  StorPool consists of two parts wrapped in one package - a server and
+a client.  The StorPool server allows a hypervisor to act as a storage node,
+while the StorPool client allows a hypervisor node to access the storage pool
+and act as a compute node.  In OpenStack terms the StorPool solution allows
+each hypervisor node to be both a storage and a compute node simultaneously.
+
+Use Cases
+---------
+
+As a Deployer, I want to be able to attach StorPool volumes managed by Cinder
+to my instances for persistent storage, taking advantage of StorPool's
+performance and scalability during the instance operation, instant attachment
+of the volume to the hypervisor at instance startup, and seamless migration of
+the instance to a different hypervisor.
+
+Project Priority
+----------------
+
+None.
+
+Proposed change
+===============
+
+The proposed driver will make use of the StorPool API (based on JSON over HTTP)
+to attach and detach volumes defined in the StorPool cluster and already known
+to Cinder.
+
+Alternatives
+------------
+
+None.
+
+Data model impact
+-----------------
+
+None.
+
+REST API impact
+---------------
+
+None.
+
+Security impact
+---------------
+
+None.
+
+Notifications impact
+--------------------
+
+None.
+
+Other end user impact
+---------------------
+
+None.
+
+Performance Impact
+------------------
+
+The requests to attach or detach a volume will be passed on to the StorPool
+JSON-over-HTTP API.
+
+Other deployer impact
+---------------------
+
+None.
+
+Developer impact
+----------------
+
+None.
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  Peter Penchev <openstack-dev@storpool.com>
+
+Other contributors:
+  None
+
+Work Items
+----------
+
+* Write the nova.virt.libvirt.storpool driver to attach and detach volumes.
+
+* Write tests for the StorPool driver.
+
+* Provide a CI setup for the StorPool driver.
+
+Dependencies
+============
+
+The StorPool driver for Cinder for handling StorPool volumes:
+https://blueprints.launchpad.net/cinder/+spec/storpool-block-driver
+
+Testing
+=======
+
+Since the test setup requires an operational StorPool cluster, the unit tests
+will mostly use mocking to simulate the operations.  A separate continuous
+integration environment will be set up by StorPool and access to it will be
+provided for running automated CI tests.
+
+Documentation Impact
+====================
+
+Using the StorPool driver will be documented.
+
+References
+==========
+
+The StorPool distributed storage software: http://storpool.com/