AWS RDS Multi AZ deployment and Read Replica

RDS makes it easy to set up, operate, and scale a relational database in the cloud. It comes up with many features that makes customers like easier. In this article, we will discuss somewhate related concepts Multi AZ and read replica. This should help you answer multi AZ and read replica related questions.

Amazon RDS Multi-AZ deployment

  • In a Multi-AZ deployment, Amazon RDS automatically provisions and maintains a synchronous standby replica in a different Availability Zone.
  • Multi-AZ deployment provides high availability, durability and automatic failover support
  • RDS automatically provisions and manages a synchronous standby instance in a different AZ
  • standby replica can’t be used to serve read traffic.
  • RDS automatically fails over to the standby so that database operations can resume quickly without administrative intervention
  • Failover mechanism automatically changes the DNS record of the DB instance to point to the standby DB instance.
  • Running a DB instance with high availability can enhance availability during planned system maintenance, and help protect your databases against DB instance failure and Availability Zone disruption

Multi AZ

Amazon RDS Read Replicas

  • Amazon RDS uses DB engines’ built-in replication functionality to create a special type of DB instance called a read replica from a source DB instance.
  • The source DB instance becomes the primary DB instance.
  • Updates made to the primary DB instance are asynchronously copied to the read replica.
  • You can reduce the load on your primary DB instance by routing read queries from your applications to the read replica.
  • When you create a read replica, you first specify an existing DB instance as the source. Then Amazon RDS takes a snapshot of the source instance and creates a read-only instance from the snapshot. Amazon RDS then uses the asynchronous replication method for the DB engine to update the read replica whenever there is a change to the primary DB instance. The read replica operates as a DB instance that allows only read-only connections. Applications connect to a read replica the same way they do to any DB instance. Amazon RDS replicates all databases in the source DB instance.

read Replica

Comparison

Multi-AZ deployments Multi-Region deployments Read replicas
Purpose is Availability Purpose is DR & local performance Purpose is Scalability
Non-Aurora:Syncronous & Aurora Asynchronous Replication Asynchronous Replication Asynchronous Replication
Always span at least two Availability Zones within a single region Each region can have a Multi-AZ deployment Can be within an Availability Zone, Cross-AZ, or Cross-Region
utomatic failover to standby (non-Aurora) or read replica (Aurora) when a problem is detected Aurora allows promotion of a secondary region to be the master Can be manually promoted to a standalone database instance (non-Aurora) or to be the primary instance (Aurora)

References

https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Concepts.MultiAZ.html https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_ReadRepl.html https://aws.amazon.com/rds/features/multi-az/

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