Administering an ISP Installation

Defining Clustering

Clustering involves grouping independent servers and managing them as a single system. The minimum requirements for a server cluster include the following:

Two (or more) servers connected by a network
Cluster management software, such as Network Load Balancing or Cluster Service

The cluster management software performs the following tasks:

Detects failure on any computer in the cluster
Recovers from any failure or server overload
Balances the load of incoming requests over all the servers in the cluster
Manages the servers as a single system

Clustering servers together into one system offers certain advantages:

Always Available to Handle Incoming Requests Because incoming requests from clients can be balanced among several servers, the likelihood of overloading one server is diminished. If one server becomes overloaded and fails, load balancing can redistribute requests among the remaining servers, without interruption to clients.
Easier to Manage Instead of managing each server separately, you can manage them as a unit.
Greater Scalability You can easily add more servers to the cluster or upgrade existing ones without interruption to incoming client requests.