Azure SQL Database Premium tier supports multiple redundant replicas for each database that are automatically provisioned in the same datacenter within a region. This design leverages the SQL Server AlwaysON technology and provides resilience to server failures with 99.99% availability SLA and RPO=0. With the introduction of Azure Availability Zones, we are happy to announce that SQL Database now offers built-in support of Availability Zones in its Premium service tier. By placing individual database replicas in different availability zones, it makes Premium databases resilient to a much larger set of failures, including catastrophic datacenter outages. The built-in support of Availability Zones further enhances the High Availability (HA) solutions in Azure SQL Database. For more information see High-availability and Azure SQL Database.
To take advantage of this capability, you simply select the zone redundant option during database or elastic pool creation. You can also enable it for existing databases or pools. Once enabled, if availability zones are supported in the region where your database or pool is deployed, Azure SQL will automatically reconfigure the database or pool without any downtime.
You can use the Azure portal to configure a database to be zone redundant as illustrated on the following diagram.
The preview of zone redundant Premium databases and pools is currently available in Central US, West Europe, and France Central, with additional regions added over time.