Components of High Availability

High availability is a buzzword that many application and hardware vendors like to throw around to get you to purchase their product. Many different options are available to achieve high availability, and there also seem to be a number of different definitions and variations that help vendors sell their products as high availability solutions.

But when it comes down to it, high availability is simply providing services with maximum uptime by avoiding unplanned downtime. Often disaster recovery (DR) is also closely lumped into discussions of high availability, but DR encompasses the business and technical processes that are used to recover once a disaster has happened.

Defining a high availability plan usually starts with a Service Level Agreement (SLA). At its base, an SLA defines the services and metrics that must be met for availability and performance of an application or service. Often an SLA is created for an IT department or service provider to provide a specific level of service.