Amazon RDS now offers Multi-AZ support for Amazon RDS for SQL Server in the Asia Pacific (Seoul) AWS Region. This unique high availability option leverages SQL Server Mirroring technology with additional improvements to meet the requirements of enterprise-grade production workloads running on SQL Server. The Multi-AZ deployment option provides enhanced availability and data durability by automatically replicating database updates between two AWS Availability Zones. Availability Zones are physically separate locations with independent infrastructure engineered to be insulated from failures in other Availability Zones.
Source: amazon.com