Microsoft SQL Server 2012 Bible

High Availability and Scalability

The goal of SQL Database is to provide a highly available and scalable cloud database service built on SQL Server technologies. This database service is designed to include built-in high availability and fault tolerance with zero physical administration.

Think about this for a minute. How would you like to spend less time worrying about the physical aspects of your SQL Server and more time focusing on the things you really like to do, such as database development? This is exactly what SQL Database provides. The following sections discuss how SQL Database provides a managed service that has a 99.9 percent monthly SLA with high availability and scalability.

High Availability

SQL Database strives to maintain 99.9 percent availability, achieved by using commodity hardware that can be quickly replaced if hardware or drive failure occurs. However, more important, when you create a database in SQL Database, you actually get three databases: one primary and two replicas. These three databases are always in sync. If the primary fails, it is taken offline and one of the two replicas is designated as the new primary and another replica created. This automatic failover exists to optimize availability for your application.

Microsoft currently has six data centers world-wide dedicated to supporting the Windows Azure platform. Two data centers are located in the United States, two are located in Europe, and two are located in Asia.

Scalability

A huge benefit ...