The Importance of Redundancy

Amongst possible types of failures, process, node, and media failures as well as human errors can be protected by local high availability solutions. Local physical disasters can be protected by geographically, distributed disaster recovery solutions.

To solve the high availability problem, a number of technologies and best practices are needed. The most important mechanism is redundancy. High availability comes from redundant systems and components. Local high availability solutions can be categorized, by their level of redundancy.

Active-passive solutions deploy an active instance that handles requests and a passive instance that is on standby. In addition, a heartbeat mechanism is set up between these two instances. This mechanism is provided and managed through operating system vendor-specific clusterware. Generally, vendor-specific cluster agents are also available to automatically monitor and failover between cluster nodes, so that when the active instance fails, an agent shuts down the active instance completely, brings up the passive instance, and application services can successfully resume processing. As a result, the active-passive roles are now switched. The same procedure can be done manually for planned or unplanned down time. Active-passive solutions are also generally referred to as cold failover clusters.

In some instances, HA hosting may not sufficiently accomplish all your disaster prevention and redundancy goals. For example, some businesses need fault tolerant or geographical site protection from disasters. In these cases customer can leverage Empire Hosting's DNS active failover across geographically dispersed sites to ensure consistent business continuity of critical services and applications. Once HA has recovered impacted servers onto healthy hardware the DNS for critical services can be redirected.