It is similar to any traditional application, there are dependent core components that are pivotal to the functionality but not necessarily the application itself. In the case of the base OpenStack architecture, there are two core components that will be considered as the core or backbone of the cloud. The OpenStack functionality requires access to an SQL-based backend database service and an Advanced Message Queuing Protocol (AMQP) software platform. Just as with most things OpenStack related there are the most commonly used/recommended choices adopted by the OpenStack community. From a database perspective, the common choice will be MySQL and the default AMQP package is RabbitMQ. These two dependencies must be installed, configured, and functional before you can start an OpenStack deployment.

There are additional optional software packages that can also be used to provide further stability as a part of your cloud design. The information about this management software and OpenStack architecture details can be found at the following link:

http://docs.openstack.org/arch-design/generalpurpose-architecture.html