========
Overview
========

The OpenStack project is an open source cloud computing platform that supports
all types of cloud environments. The project aims for simple implementation,
massive scalability, and a rich set of features. Cloud computing experts from
around the world contribute to the project.

OpenStack provides an Infrastructure-as-a-Service (IaaS) solution through a
variety of complementary services. Each service offers an Application
Programming Interface (API) that facilitates this integration.

This guide covers step-by-step deployment of the major OpenStack services using
a functional example architecture suitable for new users of OpenStack with
sufficient Linux experience. This guide is not intended to be used for
production system installations, but to create a minimum proof-of-concept for
the purpose of learning about OpenStack.

After becoming familiar with basic installation, configuration, operation, and
troubleshooting of these OpenStack services, you should consider the following
steps toward deployment using a production architecture:

* Determine and implement the necessary core and optional services to meet
  performance and redundancy requirements.

* Increase security using methods such as firewalls, encryption, and service
  policies.

* Implement a deployment tool such as Ansible, Chef, Puppet, or Salt to
  automate deployment and management of the production environment.

.. _overview-example-architectures:

Example architecture
~~~~~~~~~~~~~~~~~~~~

The example architecture requires at least two nodes (hosts) to launch a basic
virtual machine (VM) or instance. Optional services such as Block Storage and
Object Storage require additional nodes.

.. important::

   The example architecture used in this guide is a minimum configuration, and
   is not intended for production system installations. It is designed to
   provide a minimum proof-of-concept for the purpose of learning about
   OpenStack. For information on creating architectures for specific use cases,
   or how to determine which architecture is required, see the `Architecture
   Design Guide <https://docs.openstack.org/arch-design/>`_.

.. warning::

   Once a cloud has been deployed, changing the host name of *any* node in the
   deployment is not supported. In some cases, it may be possible to remove a
   node from the deployment, and add it again under a different host name.
   Renaming a node in situ will result in problems that will require multiple
   manual fixes.

This example architecture differs from a minimal production architecture as
follows:

* Networking agents reside on the controller node instead of one or more
  dedicated network nodes.

* Overlay (tunnel) traffic for self-service networks traverses the management
  network instead of a dedicated network.

For more information on production architectures, see the `Architecture Design
Guide <https://docs.openstack.org/arch-design/>`_, `OpenStack Operations Guide
<https://wiki.openstack.org/wiki/OpsGuide>`_, and `OpenStack Networking Guide
<https://docs.openstack.org/ocata/networking-guide/>`_.

.. _figure-hwreqs:

.. figure:: figures/hwreqs.png
   :alt: Hardware requirements

   **Hardware requirements**

Controller
----------

The controller node runs the Identity service, Image service, management
portions of Compute, management portion of Networking, various Networking
agents, and the Dashboard. It also includes supporting services such as an SQL
database, message queue, and Network Time Protocol (NTP).

Optionally, the controller node runs portions of the Block Storage, Object
Storage, Orchestration, and Telemetry services.

The controller node requires a minimum of two network interfaces.

Compute
-------

The compute node runs the hypervisor portion of Compute that operates
instances. By default, Compute uses the kernel-based VM (KVM) hypervisor. The
compute node also runs a Networking service agent that connects instances to
virtual networks and provides firewalling services to instances via security
groups.

You can deploy more than one compute node. Each node requires a minimum of two
network interfaces.

Block Storage
-------------

The optional Block Storage node contains the disks that the Block Storage and
Shared File System services provision for instances.

For simplicity, service traffic between compute nodes and this node uses the
management network. Production environments should implement a separate storage
network to increase performance and security.

You can deploy more than one block storage node. Each node requires a minimum
of one network interface.

Object Storage
--------------

The optional Object Storage node contain the disks that the Object Storage
service uses for storing accounts, containers, and objects.

For simplicity, service traffic between compute nodes and this node uses the
management network. Production environments should implement a separate storage
network to increase performance and security.

This service requires two nodes. Each node requires a minimum of one network
interface. You can deploy more than two object storage nodes.

Networking
~~~~~~~~~~

Choose one of the following virtual networking options.

.. _network1:

Networking Option 1: Provider networks
--------------------------------------

The provider networks option deploys the OpenStack Networking service in the
simplest way possible with primarily layer-2 (bridging/switching) services and
VLAN segmentation of networks. Essentially, it bridges virtual networks to
physical networks and relies on physical network infrastructure for layer-3
(routing) services. Additionally, a DHCP<Dynamic Host Configuration Protocol
(DHCP) service provides IP address information to instances.

The OpenStack user requires more information about the underlying network
infrastructure to create a virtual network to exactly match the infrastructure.

.. warning::

   This option lacks support for self-service (private) networks, layer-3
   (routing) services, and advanced services such as Load-Balancer-as-a-Service
   (LBaaS) and FireWall-as-a-Service (FWaaS).  Consider the self-service
   networks option below if you desire these features.

.. _figure-network1-services:

.. figure:: figures/network1-services.png
   :alt: Networking Option 1: Provider networks - Service layout

.. _network2:

Networking Option 2: Self-service networks
------------------------------------------

The self-service networks option augments the provider networks option with
layer-3 (routing) services that enable self-service networks using overlay
segmentation methods such as Virtual Extensible LAN (VXLAN). Essentially, it
routes virtual networks to physical networks using Network Address Translation
(NAT). Additionally, this option provides the foundation for advanced services
such as LBaaS and FWaaS.

The OpenStack user can create virtual networks without the knowledge of
underlying infrastructure on the data network. This can also include VLAN
networks if the layer-2 plug-in is configured accordingly.

.. _figure-network2-services:

.. figure:: figures/network2-services.png
   :alt: Networking Option 2: Self-service networks - Service layout
