ENVS 1200 Lecture Notes - Lecture 10: Parallel Computing, Loose Coupling, Multiprocessing
13 May 2018
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ENVS 1200 Lecture 10 Notes – Clusters
Introduction
• In multiprocessing we increase processing speed by introducing multiple CPUs, or cores,
to share the processing load.
• Each core shares access to memory and to I/O resources.
• As an alternative approach, it is possible to build systems in which the computers are
tied together loosely.
• By this we mean that each computer is complete in itself, each with its own CPU,
memory, and I/O facilities.
• Data communications provide the link between the different computers.
• Such systems of computers are called loosely coupled systems.
• Some authors refer to these systems as multicomputer systems.
• Loosely coupled systems enable program and data sharing and exchange between
complete computers.
• Some loosely coupled systems share a disk resource or a small amount of memory that
can be used to communicate between the different computers.
• The determining factor that distinguishes a loosely coupled system is the autonomy of
each computer within the system complex or network.
• There are two basic methods of connecting loosely coupled computers.
• Clustered computers are connected directly together with a dedicated communication
channel or link that passes messages between machines.
• The cluster is designed to operate as a single autonomous system sharing a workload.
• Networked computers operate more independently.
• The data communication channel between machines is used to exchange and share data
and external resources, rather than to share the actual processing.
• Our focus is on clusters.
• Networks are discussed in the next part.
• A cluster is a group of loosely coupled computers configured to work together as a unit.
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