This book has been organized into various chapters that help define the use cases associated with making architectural choices related to an OpenStack cloud installation. Each chapter is intended to stand alone to encourage individual chapter readability, however each chapter is designed to contain useful information that may be applicable in situations covered by other chapters. Cloud architects may use this book as a comprehensive guide by reading all of the use cases, but it is also possible to review only the chapters which pertain to a specific use case. When choosing to read specific use cases, note that it may be necessary to read more than one section of the guide to formulate a complete design for the cloud. The use cases covered in this guide include: General purpose: A cloud built with common components that should address 80% of common use cases. Compute focused: A cloud designed to address compute intensive workloads such as high performance computing (HPC). Storage focused: A cloud focused on storage intensive workloads such as data analytics with parallel file systems. Network focused: A cloud depending on high performance and reliable networking, such as a content delivery network (CDN). Multi-site: A cloud built with multiple sites available for application deployments for geographical, reliability or data locality reasons. Hybrid cloud: An architecture where multiple disparate clouds are connected either for failover, hybrid cloud bursting, or availability. Massively Scalable: An architecture that is intended for cloud service providers or other extremely large installations. A section titled Specialized Use Cases provides information on architectures that have not previously been covered in the defined use cases. Each chapter in the guide is then further broken down into the following sections: Introduction: Provides an overview of the architectural use case. User requirements: Defines the set of user considerations that typically come into play for that use case. Technical considerations: Covers the technical issues that must be accounted when dealing with this use case. Operational considerations: Covers the ongoing operational tasks associated with this use case and architecture. Architecture: Covers the overall architecture associated with the use case. Prescriptive examples: Presents one or more scenarios where this architecture could be deployed. A Glossary covers the terms and phrases used in the book.