Aurora Read replicas for failover instead of multi - AZ
Hi, I am new to AWS and new to databases. While reading the Aurora FAQs:
"Q: How can I improve upon the availability of a single Amazon Aurora database?
You can add Amazon Aurora Replicas. Aurora Replicas in the same AWS Region share the same underlying storage as the primary instance. Any Aurora Replica can be promoted to become primary without any data loss and therefore can be used for enhancing fault tolerance in the event of a primary DB Instance failure. To increase database availability, simply create 1 to 15 replicas, in any of 3 AZs, and Amazon RDS will automatically include them in failover primary selection in the event of a database outage."
Does this mean there is no concept of multi-AZ with Aurora like with other Amazon RDS DBs ? and I can just use read replicas for availability as well as performance purposes ?
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Multi-AZ is very much applicable with Amazon Aurora. With Aurora compute and storage is decoupled. Storage will always get replicated across 3 AZs, regardless of you compute configuration. When you create read replicas, you can spread them across multiple AZs as well.
Read replicas in Aurora can be used not only for reads, but they also serve HA purpose. Although keep in mind that the readers will lag by several miliseconds (which is acceptable for vast majority of customers). This is a significant improvement over regular RDS multi-AZ HA, which only works as a standby, and doesn't allow reads.
So, to summarize: Multi-AZ HA works on both compute and storage layers with Aurora, and the secondary nodes can serve as HA as well as read replicas.
