High availability is a computing concept whereby a server fulfilling a user’s request does so with the utmost reliability, by using built-in failover mechanisms that mitigate against the effects of any one component failing.

High-traffic websites must support hundreds of thousands, if not millions, of users in a fast, reliable manner. IT organizations support these large volumes by pooling servers into a group (sometimes called a server farm). A load balancer sits in front of the server group and routes traffic to individual servers in a way that maximizes efficiency. With multiple servers acting as a single unit, companies can ensure that if a single server goes down, the user’s request is routed to the next available server. In such a manner, users don’t receive an outright error or failure. This is known as a high-availability configuration.

High availability is often measured in terms of the percentage of the time that service is available to clients. A 99.999% uptime rating, also known as “five nines,” translates to approximately 5&nsp;minutes of downtime per year.

The load balancer or application delivery controller (ADC) is the key component that ensures high availability. The load balancer intelligently routes client requests to the right server, in a manner that maximizes performance and capacity utilization while sending requests only to servers that are online. Advanced load balancers can even routinely monitor the health of servers, bring additional servers online when traffic spikes, and reboot a server that is down.

How Can NGINX Plus Help?

NGINX Plus and NGINX are the best-in-class web server and load balancing solutions used by high-traffic websites such as Dropbox, Netflix, and Zynga. More than 266 million websites worldwide, including the majority of the 100,000 busiest websites, rely on NGINX Plus and NGINX to deliver their content quickly, reliably, and securely.

NGINX Plus is a software-based load balancing solution that provides high availability at a considerably lower expense than hardware solutions with similar capabilities.