Definition
A high availability (HA) cluster guarantees continuous system availability and operation with minimal downtime, even during hardware or software failures. This configuration is essential for services that require continuous operations, such as data centers, hospitals, or banks.
How High Availability Cluster Works
- Redundancy: The HA cluster is based on the principle of redundancy. It consists of two or more nodes configured to perform identical tasks. If one node fails, another can step in without interrupting the service. The nodes share data access to maintain consistent operations.
- Monitoring: Each node’s status is continuously monitored to detect failures promptly. This includes checking network connectivity, the hardware’s health, and the applications’ status. If an issue is found, the cluster management software resolves it.
- Failover: This is switching operations from the malfunctioning node to the standby node. If the cluster software detects a failure, it will automatically reassign the malfunctioning node’s tasks to another node in the cluster. The failover process must be swift to reduce downtime and ensure continuous service availability.
- Load balancing: Certain HA clusters evenly balance incoming requests or workloads across all nodes, ensuring no single node is overwhelmed. This enhances the service’s performance and reliability.
- Synchronization: Data and configurations are synchronized throughout the cluster to ensure all nodes can assume control from one another at any time. This helps ensure that the standby node can provide the same service as the failover node using the most recent data.
- Cluster management software: The cluster management software oversees the operations of an HA cluster. It coordinates monitoring, failover, load balancing, and synchronization. Moreover, it decides when to trigger a failover and chooses the appropriate node to assume services based on established policies and the cluster’s current status.