Merge "Adds restrictions into openstack.yaml file for roles"

docs/develop/nailgun/customization/roles.rst

@@ -34,4 +34,80 @@ section. It defines role name, description and conflicts with other roles::
 on the same node. In this example, "controller" and "compute" roles cannot be
 combined.
 
+Roles restrictions
+------------------
+
+You should take the following restrictions for the role into consideration:
+
+#. Controller
+
+   * There should be at least one controller. The `Not enough deployed controllers` error
+     occurs when you have 1 Controller installed and want to redeploy that controller.
+     During redeployment, it will be taken off,
+     so for some time the cluster will not have any operating controller, which is wrong.
+
+   * If we are using simple multinode mode, then we cannot add more than one controller.
+
+   * In HA mode, we can add as much as possible controllers, though it is recommended to add at least 3.
+
+   * Controller role cannot be combined with compute.
+
+  #. Compute
+
+  * It is recommended to have at least one compute in non-vCenter env (https://bugs.launchpad.net/fuel/+bug/1381613 :
+    note that this is a bug in UI and not yaml-specific).
+    Beginning with Fuel 6.1, no vCenter-related limitations are longer present.
+
+  * Computes cannot be combined with controllers.
+
+  * Computes cannot be added if vCenter is chosen as a hypervisor
+
+
+#. Cinder
+
+  * It is impossible to add Cinder nodes to an environment with Ceph RBD.
+
+  * At least one Cinder node is recommended
+
+  * Cinder LVM needs to be enabled on the *Settings* tab of the Fuel web UI
+
+
+#. MongoDB
+
+  * Cannot be added to already deployed environment.
+
+  * Can be added only if Ceilometer is enabled.
+
+  * Cannot be combined with Ceph OSD and Compute.
+
+  * For a simple mode there has to be 1 Mongo node, for HA at least 3.
+
+  * It is not allowed to choose MongoDB role for a node if external MongoDB setup is used.
+
+
+#. Zabbix
+
+  * Only available in experimental ISO.
+
+  * Cannot be combined with any other roles.
+
+  * Only one Zabbix node can be assigned in an environment.
+
+
+#. Ceph
+
+  * Cannot be used with Mongo and Zabbix.
+
+  * Minimal number of Ceph nodes is equal to
+    the `Ceph object replication factor` value from the *Settings* tab of the Fuel web UI
+
+  * Ceph cannot be added if vCenter is chosen as a hypervisor
+    and `volumes_ceph`, `images_ceph` and `ephemeral_ceph` settings are all False
+
+
+#. Ceilometer
+
+  * Either a node with MongoDB role or external MongoDB turned on is required .
+
+
 .. _openstack.yaml: https://github.com/stackforge/fuel-web/blob/master/nailgun/nailgun/fixtures/openstack.yaml