Always on Fail-over cluster

High availability and redundancy are key requirements in todayʼs IT infrastructure and Always On Failover Clustering Instances (FCIs) are one of the best options to deliver it. Always On FCI is a type of failover clustering that enables a high-availability solution to provide continuous availability of data and applications for mission-critical enterprise workloads.

 Itʼs used by businesses to ensure that their data and applications are always up and running so that business operations arenʼt disrupted due to any unexpected downtime. It does this by creating one or more copies (instances) of your databases on different servers and automatically failing over to an instance if the primary instance becomes unavailable. FCIs are implemented using Windows Server Failover Clustering (WSFC), which is a feature of the Windows operating system that allows you to create a cluster of servers that can provide high availability for applications and services. FCIs use WSFC to provide high availability for SQL Server instances.

 When you create an FCI, you install a copy of the SQL Server on each node in the cluster. One of the nodes is designated as the primary node, and the other nodes are designated as secondary nodes. The primary node hosts the primary instance of the SQL Server, and the secondary nodes host secondary instances of the SQL Server.

If the primary node fails, WSFC will automatically failover to one of the secondary nodes, which will become the new primary node and host the primary instance of the SQL Server. This process is transparent to users and clients, who will continue to access the primary instance of the SQL Server as if nothing had happened. FCIs provide a highly available and resilient environment for your SQL Server instances by automatically failing over to a secondary instance in the event of a failure. This can help improve your database environment's reliability, performance, and uptime.

 

How does Always On Failover Clustering Instances work?

Always On FCI works by setting up two or more servers to host the same applications and share the same data. If one server encounters an issue or goes down, the other server automatically takes over and provides the same services and data. This ensures that itʼs always available, even during an outage.

This setup is highly reliable because a single system monitors and manages the two servers. If the primary server fails, the other server will be automatically triggered to take over without any manual intervention. This means that the data and applications remain available, so your business operations remain uninterrupted.