High Availability Cluster

A high-availability cluster, commonly known as an HA clusters or a failover cluster, is a highly redundant multiple server network that makes it possible for critical server applications such as databases to run 24/7, 365 days a year. If one server in a high availability cluster fails, the mission-critical app is immediately restarted on another server the moment the fault is detected.

According to the Microsoft Network Developer Glossary, high availability is “the ability of a system or device to be usable when it is needed.  As a percentage, high availability is the actual service time divided by the required service time…a network often is considered highly available if it achieves 99.999 percent network uptime.”

The extreme redundancy found in high availability clusters is achieved by sophisticated software and hardware fault detection schemes as well as comprehensive pre-failover preparations. Clustering software typically pre-configures the node of the new server so the application can be started instantly upon failover. This pre-configuration might include importing and mounting file systems, configuring network hardware and making sure all supporting apps are running in the background.

High availabilityclusters are typically utilized for e-mail or database servers, as well as file sharing. HA clusters can be deployed in a server farm in a single physical facility, or as “geoclusters” installed at geographically dispersed location for additional network resiliency.

Idera’s SQL Safe backup solution is designed to work in high availability cluster environments. Furthermore, SQL Safe components are designed to operate in active-passive or active-active cluster configurations.