High Availability

High availability refers to systems that are designed to provide continuous uptime and avoid any disruption of services. High availability systems have built-in redundancy to minimize or eliminate single points of failure. If one component fails, a redundant component takes over seamlessly without any noticeable interruption for end users.

To achieve high availability, systems are often set up across multiple servers or data centers. Load balancers distribute traffic so if one server goes down, traffic is instantly routed to other available servers. Data is replicated across locations to prevent data loss. Monitoring tools watch for failures and can automatically failover to backup systems. High availability systems aim for 99.999% uptime, allowing for only about 5 minutes of downtime per year. Popular techniques include clustering, failover, replication, and redundancy. For example, a highly available web application may run across six servers with load balancing and real-time data replication, achieving no visible downtime even if one or two servers fail.