Amazon RDS: can databases be setup in replicaton mode?

Question

I am studying the new Amazon RDS product and it seems it can be scaled only vertically (i.e. put a stronger server).

Did anyone see a possibility to configure multiple instances so that one is master and the other/s is/are replication slaves?

Answer 1

Same question asked (and answered) here http://developer.amazonwebservices.com/connect/thread.jspa?threadID=37823

Looks like there are plans for Master-Master HA or similar but that's not the same a replicated scale-out offering.

Answer 2

According to the FAQ it is possible now, see http://aws.amazon.com/rds/faqs/#86 :

Q: What types of replication does Amazon RDS support and when should I use each?

Amazon RDS provides two distinct replication options to serve different purposes.

If you are looking to use replication to increase database availability while protecting your latest database updates against unplanned outages, consider running your DB Instance as a Multi-AZ deployment. When you create or modify your DB Instance to run as a Multi-AZ deployment, Amazon RDS will automatically provision and manage a “standby” replica in a different Availability Zone (independent infrastructure in a physically separate location). In the event of planned database maintenance, DB Instance failure, or an Availability Zone failure, Amazon RDS will automatically failover to the standby so that database operations can resume quickly without administrative intervention. Multi-AZ deployments utilize synchronous replication, making database writes concurrently on both the primary and standby so that the standby will be up-to-date in the event a failover occurs. While our technological implementation for Multi-AZ DB Instances maximizes data durability in failure scenarios, it precludes the standby from being accessed directly or used for read operations. The fault tolerance offered by Multi-AZ deployments make them a natural fit for production environments; to learn more about Multi-AZ deployments, please visit this FAQ section.

If you are looking to take advantage of MySQL 5.1’s built-in replication to scale beyond the capacity constraints of a single DB Instance for read-heavy database workloads, Amazon RDS makes it easier with Read Replicas. You can create a Read Replica of a given “source” DB Instance using the AWS Management Console or CreateDBInstanceReadReplica API. Once the Read Replica is created, database updates on the source DB Instance will be propagated to the Read Replica. You can create multiple Read Replicas for a given source DB Instance and distribute your application’s read traffic amongst them. Unlike Multi-AZ deployments, Read Replicas use MySQL 5.1’s built-in replication and are subject to its strengths and limitations. In particular, updates are applied to your Read Replica(s) after they occur on the source DB Instance (“asynchronous” replication), and replication lag can vary significantly. This means recent database updates made to a standard (non Multi-AZ) source DB Instance may not be present on associated Read Replicas in the event of an unplanned outage on the source DB Instance. As such, Read Replicas do not offer the same data durability benefits as Multi-AZ deployments. While Read Replicas can provide some read availability benefits, they and are not designed to improve write availability.

With Amazon RDS, you can use Multi-AZ deployments and Read Replicas in conjunction to enjoy the complementary benefits of each. You can simply specify that a given Multi-AZ deployment is the source DB Instance for your Read Replica(s). That way you gain both the data durability and availability benefits of Multi-AZ deployments and the read scaling benefits of Read Replicas.