Add instructions on how to provision a custom Cinder backend

Change-Id: I8047591e32ed50537f435e86c64e87d6cc696a20

doc/source/advanced_deployment/advanced_deployment.rst

@@ -18,6 +18,7 @@ In this chapter you will find advanced deployment of various |project| areas.
    network_isolation
    network_isolation_virt
    deploy_manila
+   cinder_custom_backend
    cinder_netapp
    neutron_midonet
    ssl

doc/source/advanced_deployment/cinder_custom_backend.rst

@@ -0,0 +1,69 @@
+Configuring Cinder with a Custom Unmanaged Backend
+==================================================
+
+This guide assumes that your undercloud is already installed and ready to
+deploy an overcloud.
+
+Adding a custom backend to Cinder
+---------------------------------
+
+It is possible to provide the config settings to add an arbitrary and
+unmanaged backend to Cinder at deployment time via Heat environment files.
+
+Each backend is represented in `cinder.conf` with a ``stanza`` and a
+reference to it from the `enabled_backends` key. The keys valid in the
+backend ``stanza`` are dependent on the actual backend driver and
+unknown to Cinder.
+
+For example, to provision in Cinder two additional backends one could
+create a Heat environment file with the following contents::
+
+  parameter_defaults:
+    ExtraConfig:
+      cinder::config::cinder_config:
+          netapp1/volume_driver:
+                  value: cinder.volume.drivers.netapp.common.NetAppDriver
+          netapp1/netapp_storage_family:
+                  value: ontap_7mode
+          netapp1/netapp_storage_protocol:
+                  value: iscsi
+          netapp1/netapp_server_hostname:
+                  value: 1.1.1.1
+          netapp1/netapp_server_port:
+                  value: 80
+          netapp1/netapp_login:
+                  value: root
+          netapp1/netapp_password:
+                  value: 123456
+          netapp1/volume_backend_name:
+                  value: netapp_1
+          netapp2/volume_driver:
+                  value: cinder.volume.drivers.netapp.common.NetAppDriver
+          netapp2/netapp_storage_family:
+                  value: ontap_7mode
+          netapp2/netapp_storage_protocol:
+                  value: iscsi
+          netapp2/netapp_server_hostname:
+                  value: 2.2.2.2
+          netapp2/netapp_server_port:
+                  value: 80
+          netapp2/netapp_login:
+                  value: root
+          netapp2/netapp_password:
+                  value: 123456
+          netapp2/volume_backend_name:
+                  value: netapp_2
+      cinder_user_enabled_backends: ['netapp1','netapp2']
+
+This will not interfere with the deployment of the other backends managed by
+TripleO, like Ceph or NFS and will just add these two to the list of the
+backends enabled in Cinder.
+
+Remember to add such an environment file to the deploy commandline::
+
+    openstack overcloud deploy [other overcloud deploy options] -e ~/my-backends.yaml
+
+.. note::
+
+    The :doc:`extra_config` doc has more details on the usage of the different
+    ExtraConfig interfaces.