Redundancy
6 copies across 3 AZs to tolerate AZ+1 failures.
- write quorum of 4/6
- read quorum of 3/6 (only for repair)
References
- https://assets.amazon.science/dc/2b/4ef2b89649f9a393d37d3e042f4e/amazon-aurora-design-considerations-for-high-throughput-cloud-native-relational-databases.pdf (https://www.amazon.science/publications/amazon-aurora-design-considerations-for-high-throughput-cloud-native-relational-databases)
- https://pages.cs.wisc.edu/~yxy/cs839-s20/papers/aurora-sigmod-18.pdf (https://www.amazon.science/publications/amazon-aurora-on-avoiding-distributed-consensus-for-i-os-commits-and-membership-changes)