A failover cluster is a group of independent computers that work together to increase the availability and scalability of clustered roles (formerly called clustered applications and services).

A failover cluster usually includes a storage unit that is physically connected to all the servers in the cluster, although any given volume in the storage is only accessed by one server at a time. The following diagram shows a two-node failover cluster connected to a storage unit.

Log Shipping : https://youtu.be/S1SaSJZtYzA
Database Mirroring : https://youtu.be/DlukbLQCkZ0 and https://youtu.be/WcnHvTIbxJA