[HENARRY JAYA]

It is a group of servers that have all of the same applications and services installed. It requires the Advanced or Datacenter versions of Windows Server which support clustering.
These versions allow you to install the clustering service. There should be high-capacity, high-throughput network and data connections between the member servers and shared storage.

What makes it desirable is that it allows services and applications that fail on one member of the cluster to be transferred automatically to another cluster member. Simply put, it is fault-tolerance for the application layer.
A clustered approach to web hosting can take the sites to a new level as it overcomes the limitations of one physical server. Even compared to the finest dedicated server plans a clustered approach is still far superior. Grid web hosting technology or the clustered dedicated servers allows sharing of processing powers amongst many servers, distributed in real time. This means that the websites are powered by a very powerful and inexhaustible source; it is because even the largest customer cannot take more than a tiny fraction of the large server pool. The other benefit is that, even if one server is under threat thee are lots of back us available and the other servers are available to share the load.