High availability (HA) is a characteristic of a system that aims to ensure an agreed level of operational performance, usually uptime, for a higher than normal period
A high availability cluster is a group of interconnected servers that work together as a single system to ensure continuous availability of critical applications and services
A computer cluster is a set of computers that work together so that they can be viewed as a single system
Clustering can be categorized primarily into two types: Active-Active and Active-Passive.
Active-Active clusters involve multiple nodes all handling requests simultaneously. This not only provides redundancy but also enhances the performance of the system by distributing the load.
Active-Passive clusters, on the other hand, consist of active nodes and standby nodes where the standby nodes only come into play if the active ones fail.