Here's why clustering is important in computer architecture;
Absolute scalability: It is possible to create large clusters that far surpass the power of even the largest standalone machines.
Incremental scalability: A cluster is configured in such a way that it is possible to add new systems to the cluster in small increments. Thus, a user can start out with a modest system and expand it as needs grow, without having to go through a major upgrade in which an existing small system is replaced with a larger system.
High availability: Because each node in a cluster is a standalone computer, the failure of one node does not mean loss of service.
Superior price/performance: By using commodity building blocks, it is possible to put together a cluster with equal or greater computing power than a single large machine, at much lower cost.