SQL Server Always On Failover Cluster Instances (FCI)

A Failover Cluster Instance (FCI) is a single instance of SQL Server that is installed across Windows Server Failover Clustering (WSFC) nodes. On the network, an FCI appears to be an instance of SQL Server running on a single computer, but the FCI provides failover from one WSFC node to another, if the current node becomes unavailable.

Windows Failover Cluster relies on shared storage. FCI supports storage solutions such as WSFC cluster disks (iSCSI, Fiber Channel, and so on) and server message block (SMB) file shares. When a SQL Server instance is installed on the cluster, Milestone and system databases are required to be on the shared storage. Note that this means that your storage is a single point of failure, so the databases should be backed up elsewhere.

Shared storage allows the cluster to move the SQL Server instance to any node in the cluster. This can be done either manually, or automatically if one of the nodes is having a problem. There is only one copy of the data, but the network name and SQL Server service for the instance can be made active from any cluster node.

A failover cluster gives you the ability to have all the data for a SQL Server instance installed in a shared storage that can be accessed from different servers. It will always have the same instance name, IP address and port and logins, therefore XProtect Corporate and XProtect Expert will always know where to access the data.

This document provides a general outline of FCI. Refer to the Microsoft documentation(https://msdn.microsoft.com/en-us/library/ms189134) for more detailed information.