Introduction to High-Availability Clusters On Linux And Other Systems

Active-Active clusters have an added feature on top of active-passive clusters - load balancing.
Load balancing may be done at the DNS level. This is useful for TCP-based applications, where connections are (normally) long-lived.
It may be done at the router level, in case of a completely stateless protocol.
It may be done at the application level, in case the computations take much longer than the network communications.
Of-course, in case one of the nodes crashes, other nodes need to take over the clients it serviced.

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