Amazon’s cloud arm said Tuesday that it has added a Multi-AZ deployment option to its MySQL 5.1-based Relational Database Service (RDS) so users can now replicate database instances to multiple, geographically dispersed Amazon Availability Zones and enhance availability and data durability.

Amazon positions the move against the on-premise use of MySQL claiming that “true reliability, availability and data durability have been out of reach” for such users “since running in multiple data centers can be complex and costly.”

The new widgetry will work with existing RDS DB instances complements of a single API call and automatically create an identical up-to-date copy (“synchronous replica”) of a DB Instance in a separate Availability Zone.

It means Amazon RDS will failover to the standby during planned database maintenance like patching or instance size scaling and de-scaling or any unplanned service disruption.

Amazon’s database services chief Raju Gulabani claims it dramatically reduces database downtime without requiring additional work from customers and provides the fault tolerance required by mission-critical applications.

NASA Jet Propulsion Lab is reportedly going to expand its use of RDS because Multi-AZ deployments meet its cross-data center redundancy, synchronous replication and transparent failover requirements.

Amazon also anticipates adding a feature called Read Replicas in the next few months that’s supposed to help folks with read-heavy database loads scale beyond the capacity constraints of a single DB Instance by letting them create additional DB Instance replicas to handle this incoming read traffic.

It says they will be able to associate Read Replicas with Multi-AZ deployments for both read scaling and enhanced DB Instance reliability.

Multi-AZ users will pay double RDB prices of anywhere from 22 cents-$6.20 an hour depending on the size of the instance plus 20 cents a gigabyte a month for storage and 10 cents per million requests for I/O.