Chapter 5. Clusters and Massively Parallel Machines
In this chapter we will look at both clusters and massively parallel machines, starting with clusters. Both these architectures are often referred to as being loosely-coupled, a term based on the observation that the processors in one node do not have any close link with the processors in another node—processors in different nodes do not share memory (in general, although some clusters do support shared memory), and each node runs its own copy of the operating system. Such unshared-memory systems are also sometimes called NORMA, for No Remote Memory Access.
The concept of a cluster was introduced towards the end of the 70s, by Tandem with its Guardian systems, and was further exploited ...