System design ensuring minimal downtime through redundancy and automatic failover.
High Availability (HA) refers to systems designed to remain operational with minimal downtime—typically measured as 99.9% (8.7 hours/year downtime) to 99.999% (5.25 minutes/year) uptime. HA is achieved through redundancy (eliminating single points of failure), automatic failover, load balancing, and robust monitoring. HA design considers hardware, software, network, and human factors. HA comes with cost—more redundancy means higher expense—so it's typically reserved for critical systems.
Why It Matters
The DSC Perspective:
HA keeps critical systems running. Understand what availability level your systems actually provide versus what you need. Not everything needs 99.99% availability—but know what does.