Is redundancy and fail over are same?

Failover and redundancy are related concepts in computer systems, but they are not exactly the same.

Redundancy refers to the presence of duplicate components within a system, whether in hardware (such as multiple servers) or software (such as data backups). Redundancy acts as a safety net, providing backup resources in case a primary component fails.

 

Failover, on the other hand, is the process of automatically switching to a redundant component when the primary one fails. It's the mechanism that ensures the continuity of system operations despite the failure of a primary component.

 

In essence, redundancy provides the infrastructure necessary for failover to function effectively, but failover is the specific action taken when a failure occurs.

 

Example 1: Car and a spare tyre example.

Redundancy (Spare Tire): In the context of a car, redundancy would be having a spare tire in addition to the four tires already mounted on the vehicle. This spare tire serves as a backup or duplicate component in case one of the primary tires gets punctured or fails. Redundancy ensures that there's an extra tire available to maintain the functionality of the vehicle even in the event of a tire failure.

 

Failover (Using the Spare Tire): Failover, in the context of the car scenario, would be the process of switching to the spare tire when one of the primary tires gets punctured. When a tire punctures while driving, you pull over to the side of the road and initiate the failover process by replacing the punctured tire with the spare tire. This failover action ensures that the car can continue its journey despite the tire failure, maintaining operational continuity.

 

Example 2: Primary and secondary database servers.

Let me explain it with below example, where I have two database servers (one is primary and the other is secondary).

 

Redundancy: The database system consists of two servers - a primary and a secondary. Both servers are configured to hold the same data, ensuring data integrity and availability.

 

Failover: Failover is the process of automatically switching to a redundant component when the primary one fails. In this case, when the primary database server goes down, the system detects the failure and initiates failover. The secondary server is then promoted to the primary role, taking over the responsibilities of serving database requests. This failover process should be automatic and swift to minimize downtime and ensure uninterrupted service to the application server.

 

Example 3: Internet Service Providers (ISPs)

ISPs often implement redundancy and failover mechanisms in their network infrastructure. Redundancy may involve having multiple network paths or links between routers to ensure continuous connectivity. Failover occurs when one network path or link fails, and traffic is automatically rerouted through alternate paths to maintain internet connectivity for users.

 

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