I want to improve fault tolerance for my ElastiCache for Redis cluster. What are the benefits of Multi-AZ and automatic failover and how do I turn them on?
Benefits of Multi-AZ with automatic failover
- The main benefits of using Multi-AZ set up with automatic failover are the minimization of administrative needs and enhancing the availability of your cluster. When Multi-AZ and automatic failover are turned on, Amazon ElastiCache automatically detects failure. ElastiCache then promotes one of the replica nodes as a new primary without your involvement.
- Having both the primary and replica nodes in the same Availability Zone doesn't make your Redis replication group resilient to Availability Zone disruption. Redis clusters with Multi-AZ turned on can have nodes in different Availability Zones. In the event of Availability Zone failure, your primary node fails over to another Availability Zone if automatic failover is turned on.
- You're covered by the Amazon ElastiCache Service Level Agreement that's provided to clusters with the Multi-AZ feature turned on.
Turn on Multi-AZ with automatic failover
You can turn on Multi-AZ when creating a cluster. Or, you can modify an existing cluster with an existing replication group. For instructions, see Minimizing down time in ElastiCache for Redis with Multi-AZ.
Note: You can create your Redis cluster without turning on Multi-AZ, but this reduces fault tolerance. And, in the unlikely event of an Availability Zone failure or loss of network connectivity, the node becomes unavailable. Using ElastiCache for Redis replication together with Multi-AZ and automatic failover provides increased availability and fault tolerance. If automatic failover is turned off, you can manually failover from one Availability Zone to another. For more information, see Testing automatic failover.
Multi-AZ support/Auto failover for Amazon ElastiCache for Redis