Azure SQL Database is a general-purpose relational database, provided as a managed service. With it, you can create a highly available and high-performance data storage layer for the applications and solutions in Azure. SQL Database can be the right choice for a variety of modern cloud applications because it enables you to process both relational data and non-relational structures, such as graphs, JSON, spatial, and XML.
Azure’s Availability Capabilities
In a traditional SQL Server environment, you generally have at least two machines locally set up. These machines have exact, synchronously maintained, copies of the data to protect against a failure of a single machine or component. This environment provides high availability, but it doesn’t protect against a natural disaster destroying your datacenter.
Disaster recovery assumes that a catastrophic event is geographically localized enough to have another machine or set of machines with a copy of your data far away. In SQL Server, you can use Always On Availability Groups running in async mode to get this capability. People often don’t want to wait for replication to happen that far away before committing a transaction, so there’s potential for data loss when you do unplanned failovers.
Databases in the premium and business critical service tiers already do something very similar to the synchronization of an availability group. Databases in lower service tiers provide redundancy through storage by using a different but equivalent mechanism. Built-in logic helps protect against a single machine failure. The active geo-replication feature gives you the ability to protect against disaster where a whole region is destroyed.