In today's fast evolving business and commerce landscape, businesses need to be up all the time. Downtime equates to revenue loss and businesses are looking for ways to increase availability and improve their disaster recovery capability. IT professionals architecting solutions and the IT professionals supporting such solutions are increasingly feeling the heat from businesses to implement cutting edge technologies to achieve uptime goals. A recent incident in which NYSE was shut down caused huge losses as trading could not be done for almost four hours. This incident highlights the importance of high availability and the impact of downtime on business. There are numerous such incidents happening every day, and IT professionals have to use all the options they have in their arsenal to mitigate such risks. With this in mind, we set out to create this comprehensive book on SQL Always On Availability Groups. We have worked extensively in the field with large enterprise customers and know the challenges and issues faced by businesses and IT professionals. We have tried to share our field experiences and real life scenarios in this book. SQL Server is gaining database market share every day, and SQL Server Always On is an exciting feature being adopted and deployed by more and more Fortune 500 companies to provide high-availability and disaster recovery for their mission-critical SQL Server installations. This makes us believe that there is a sizable technical audience that this book will cater to.