Distributed computing

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Distributed computing is the process of running a single computational task on more than one distinct computer.

Introduction

This differs from cluster computing in that computers in a distributed computing environment are typically not exclusively running 'group' tasks, whereas clustered computers are usually much more tightly coupled. The difference makes distributed computing attractive because, when properly configured, it can use computational resources that would otherwise be unused. It can also make available computing resources which would otherwise be impossible. For example, the SETI@Home project uses 'idle time' on many thousands of computers throughout the world, and is able to analyze received signals that would have been impossible otherwise. Such arrangements permit handling of data that would otherwise require the power of expensive supercomputers.

Distributed computing is very attractive in part because interactive operation leaves most computers in 'idle' most of the time. The process which implements the distributed aspect (ie: that running on a machine normally devoted to other work) is usually specially designed to be a low priority process, using only computing power that would be 'wasted' anyway.

However, having a low-priority process constantly running prevents operating system power management routines from putting the processor into a low-power mode, resulting in increased electricity consumption. For some (typically recent, and high speed) CPUs, the difference can be on the order of tens of watts.

Distributed computing also often involves competition with other distributed systems. This competition may be for prestige, or it may be a means of enticing users to donate processing power to a specific project. For example, there is the so-called "stat race": a measure of what project has managed to perform the most distributed work over the past day or week. This has been found to be so important in practice that virtually all distributed computing projects offer on-line statistical analyses of their performances, updated at least daily, if not in real-time.

Distributed computing is also an active area of research with an abundant literature. The best known distributed computing conferences are The International Conference on Dependable Systems and Networks [1] and the ACM Symposium on Principles of Distributed Computing [2]. Journals include the Journal of Parallel and Distributed Computing [3].