[Docs] Pull over Cinder service overview for install

Discovered that when we migrated we forgot to bring over
the page that provides an overview of what the different
services are and how they work together.

This patch pulls that page over as well and links it to
the install guide.

Change-Id: Ic178f88d7c190c918b54da2a9815f61bbe51592e

doc/source/install/get-started-block-storage.rst

@@ -0,0 +1,36 @@
+=====================================
+Cinder Block Storage service overview
+=====================================
+
+The OpenStack Block Storage service (Cinder) adds persistent storage
+to a virtual machine. Block Storage provides an infrastructure for managing
+volumes, and interacts with OpenStack Compute to provide volumes for
+instances. The service also enables management of volume snapshots, and
+volume types.
+
+The Block Storage service consists of the following components:
+
+cinder-api
+  Accepts API requests, and routes them to the ``cinder-volume`` for
+  action.
+
+cinder-volume
+  Interacts directly with the Block Storage service, and processes
+  such as the ``cinder-scheduler``. It also interacts with these processes
+  through a message queue. The ``cinder-volume`` service responds to read
+  and write requests sent to the Block Storage service to maintain
+  state. It can interact with a variety of storage providers through a
+  driver architecture.
+
+cinder-scheduler daemon
+  Selects the optimal storage provider node on which to create the
+  volume. A similar component to the ``nova-scheduler``.
+
+cinder-backup daemon
+  The ``cinder-backup`` service provides backing up volumes of any type to
+  a backup storage provider. Like the ``cinder-volume`` service, it can
+  interact with a variety of storage providers through a driver
+  architecture.
+
+Messaging queue
+  Routes information between the Block Storage processes.

doc/source/install/index.rst

@@ -19,6 +19,7 @@ For more information, see the
 
 .. toctree::
 
+   get-started-block-storage
    index-obs
    index-rdo
    index-ubuntu