Databases
High availability (HA)
High availability is database and system design that keeps services running with minimal downtime, using replication, clustering and automatic failover.
High availability (HA) describes designing a system — often a database — so it keeps running with little or no downtime, even when a component fails. It relies on redundancy: replication keeps copies of the data, and clustering with automatic failover promotes a standby when the primary goes down.
For a business, HA is what prevents a single server failure from becoming an expensive outage that takes the whole application offline.