In this article, I will briefly introduce and explain the Failover Cluster technology in SQL Server. Failover Cluster technology of SQL Server is also an important technology providing high availability. So it is widely used in enterprise applications to give maximum service in productions systems.
Failover Cluster technology is the perfect technology to maintain the high availability service of the applications in the institutions that aim to provide the maximum level of service (Telecommunication, Banking, Government Offices, Holdings).
This technology can be defined as the ability of a single Database to be able to serve on more than one server. Thus, it provides High Availability, Maximum Service, which is one of the indispensable rules in the database world.
I would also like to mention that many people may see the Failover Cluster technology as a solution for Disaster Recovery, but it is not. Failover Cluster technology is not Disaster Recovery solution, it is a technology that provides only High Availability.
We can list the solutions offered by the SQL Server database for High Availability as follows.
- Failover Clustering
- Database Mirroring
- Data Replication
- Database Snapshot
In the Failover Cluster architecture, one of the 2 or more servers connected to each other through Windows Cluster is active and the other is passive. If the active server is unable to provide service in any case, the Failover status occurs and the Passive Node is enabled by Windows Cluster.
When application is accessing the database, the application continuously accesses the database with the Cluster IP entered without knowing which of the active passive nodes is. Cluster IP requests the currently active node which is the node that is sent to the node. When the active Node is down, the application is connected to the Passive Node in 1 second depending on the system and it is not affected. In this case, the passive node is active and admin can already do failover manually at any time.