In Conclusion

This chapter introduced the Linux Virtual Server (LVS) cluster load balancer called the LVS Director and the forwarding and scheduling methods it uses to pass incoming requests for cluster services to the nodes inside the cluster.

The forwarding methods used by the Director are called Network Address Translation, direct routing, and tunneling, or LVS-NAT, LVS-DR, and LVS-TUN respectively. Although the Director can select a different forwarding method for each node inside the cluster, most load balancers use only one type of forwarding method for all of the nodes in the cluster to keep the setup simpler. As I've discussed briefly in this chapter, an LVS-DR cluster is the best type of cluster to use when building an enterprise-class cluster.

The LVS scheduling methods were also introduced in this chapter. The Director uses a scheduling method to evenly distribute the workload across the cluster nodes, and these methods fall into two categories: fixed and dynamic. Fixed scheduling methods differ from dynamic methods in that no information about the current number of active connections is used when selecting a cluster node using a fixed method.

The next two chapters take a closer look at the LVS-NAT and LVS-DR forwarding methods.