Amazon’s Availability Zones are locations within a region that are isolated from each other (e.g., us-east-1a vs. With an Amazon RDS instance with Multi-AZ, the primary runs in one availability zone (AZ) and then replicates data to standby instances located in a different AZ. In the case of AWS, RDS coordinates this failover process. This failover process is either initiated from the replicas themselves or an external service. Some part of the system designates the replica as the new primary if the primary crashes or becomes unavailable. A primary instance of the DBMS replicates the database to a standby replica instance. The idea behind high-availability database systems is similar, and redundancy can make a system more robust and fault-tolerant against unexpected failures. When you delete a file on your laptop by accident, you first see whether there is a backup of that file. We’ll discuss how regular RDS databases achieve this first, then we’ll talk about how Aurora is different. The more interesting challenge is how to ensure that if the DBMS crashes, the system can still stay online with minimal disruption and without any data loss. If the DBMS instance crashes, you have to either wait for the instance to come back online (or start a new one) and then recover the database. Furthermore, it does not solve the downtime issue that hit the FAA. Using EBS this way is not that interesting from a database perspective because the DBMS does not know about this replication. Amazon RDS stores Elastic Block Storage (EBS) to maintain multiple copies of the files. The first is how to ensure that the database’s storage is replicated. But only 32% of production non-Aurora RDS instances are replicating to at least one standby instance. But as we describe below, we see people that don’t set up enable replication properly for their production databases.įor OtterTune’s customers, 70% of production Aurora clusters have read replicas. Since databases are the most important things in the world, we want to discuss how replication works in Relational Database Service (RDS) for both PostgreSQL and MySQL to ensure that your database continues to operate even when one of its parts fails or you get locked up. We don’t know the details about their system and how the file got corrupted in the first (e.g., bit rot, software error), but clearly the FAA’s database game was weak. Such a failure shouldn’t happen for such a service. And it shows the importance of high-availability and reliability for mission-critical systems. FAA officials said that it was an “ honest mistake that cost the country millions. An engineer then tried to replace the file with a backup but it turned out that the backup file was busted too. According to the FAA, the outage was due to a corrupt database file. On January 11, 2023, all flights in the US were grounded because of the Federal Aviation Administration (FAA) NOTAM system outage. □ Try it now on your first database for free! It uses machine learning to tune your database’s configuration knobs, indexes, and cloud settings. OtterTune is an automated optimization service for PostgreSQL and MySQL running on Amazon RDS and Aurora.
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