1.3.3 Clustered Systems
Another type of multiprocessor system is a clustered system, which gathers
together multiple CPUs. Clustered systems differ from the multiprocessor
systems described in Section 1.3.2 in that they are composed of two or more
individual systems—or nodes—joined together. Such systems are considered
loosely coupled. Each node may be a single processor system or a multicore
system. We should note that the definition of clustered is not concrete; many
commercial packages wrestle to define a clustered system and why one form
is better than another. The generally accepted definition is that clustered
computers share storage and are closely linked via a local-area network LAN
(as described in Chapter 17) or a faster interconnect, such as InfiniBand.