Original URL: http://www.theregister.co.uk/2013/11/27/amazon_read_replica_rds/

Amazon fires up worldwide Read Replicas for hosted MySQL

Write on one continent, read from replicas nearby

By Jack Clark

Posted in Cloud, 27th November 2013 14:12 GMT

Developers that use the hulking Amazon Web Services infrastructure cloud can now shift Read Replicas of data into other global data center hubs.

The new feature was announced at the web giant's re:Invent show earlier in November and has now been made available. Previously, Read Replicas could only be shifted about within available zones. Now they can be flung across continents.

Read Replicas are an Amazon creation that uses MySQL's internal replication features to brew up a special instance type that reflects changes made to a master database.

Up to five Read Replicas can be created for a single database instance, the company says. AWS admins will be charged for the data transferred out of the source region.

By allowing Read Replicas to be shifted between geophysical regions, Amazon has made it possible for developers to write into a single hosted MySQL Relational Database Service (RDS) system and then replicate elsewhere.

This saves them money, increases redundancy, and lowers latency, though the tech is not a good fit for applications that expect to efficiently handle write commands from multiple servers spread around the world.

"Cross Region Read Replicas are available for MySQL 5.6 and enable you to maintain a nearly up-to-date copy of your master database in a different AWS Region," Amazon CTO Werner Vogels wrote in a blog post that described the service.

"In case of a regional disaster, you can simply promote your read replica in a different region to a master and point your application to it to resume operations. Cross Region Read Replicas also enable you to serve read traffic for your global customer base from regions that are nearest to them."

The technology is available in all AWS regions except GovCloud, the company said.

By comparison, Google's own Compute Engine "CloudSQL" tech provides both synchronous and asynchronous replication but it does not appear to offer trans-continental copying in a relatively simple manner, as Amazon does.

Windows Azure's SQL Database is able to perform similar replication features, though it is unclear from Microsoft documentation that Redmond admins can get the granularity offered by Amazon with Read Replicas.

With the rollout of Read Replicas, Amazon has further increased the capabilities of RDS, sending a clear message to devs that if they want to get at new features they need to move off of the already deprecated AWS SimpleDB tech. ®