(Post 31/03/2006) Grid computing reflects a conceptual framework rather than a physical resource. The Grid approach is utilized to provision a computational task with administratively-distant resources. The focus of Grid technology is associated with the issues and requirements of flexible computational provisioning beyond the local (home) administrative domain.

The Global Grid Forum

The Global Grid Forum (GGF) has the purpose of defining specifications for grid computing. GGF is a collaboration between industry and academia with significant support from both.

The Globus Alliance

The Globus Alliance implements some of the standards developed at the GGF through the Globus Toolkit, which has become the de facto standard for grid middleware. As a middleware component, it provides a standard platform for services to build upon, but grid computing needs other components as well, and many other tools operate to support a successful Grid environment. This situation resembles that of TCP/IP: the usefulness of the Internet emerged both from the success of TCP/IP and the establishment of applications such as newsgroups and webpages.

Globus has implementations of the GGF-defined protocols to provide:

A number of tools function along with Globus to make grid computing a more robust platform, useful to high-performance computing communities. They include:

XML-based web services offer a way to access the diverse services/applications in a distributed environment. As of 2003 the worlds of grid computing and of web services have started to converge to offer Grid as a web service (Grid Service). The Open Grid Services Architecture (OGSA) has defined this environment, which will offer several functionalities adhering to the semantics of the Grid Service. The vision of OGSA is to describe and to build a well-defined suite of standard interfaces and behaviours that serve as a common framework for all Grid-enabled systems and applications.

Commercial grid computing offerings

Computing vendors have, in the 2000s, begun to offer grid solutions which are either based on the Globus Toolkit, or their own proprietary architecture. Confusion remains: in that vendors may badge their computing on demand or cluster offerings as grid computing.

Key vendors in grid computing:

Conceptual Framework

Grid computing reflects a conceptual framework rather than a physical resource. The Grid approach is utilized to provision a computational task with administratively-distant resources. The focus of Grid technology is associated with the issues and requirements of flexible computational provisioning beyond the local (home) administrative domain.

Historical sweep

Like the Internet, the Grid concept evolved from the computational needs of 'big science'. The Internet was developed to meet the need for a common communication medium between large, federally funded, computing centers. These communication links led to resource and information sharing between these centers and eventually to provide access to them for additional users. Ad hoc resource sharing 'procedures' among these original groups pointed the way toward standardization of the protocols needed to communicate between ANY administrative domain. The current Grid technology can be viewed as an extension or application of this framework to create a more generic resource sharing context.

The non-profit SETI@home project is one of the most well-known scientific causes designed to make use of idle CPU cycles even though it was not the first to pioneer the technique (other non-profit projects like distributed.net preceded SETI@home). These programs generally run in the background or as a screensaver when the user does not use the entire computing power of the PC. Many such projects have made progress in fields that would have otherwise taken prohibitive investment or a delay in/on results.

Virtual Organization

A Grid environment is created to address resource needs; the use of that resource(s) (ie. CPU cycles, disk storage, data, software programs, peripherals, etc.) is usually characterized by its availability outside of the context of the local administrative domain. This 'external provisioning' approach entails creating a new administrative domain referred to as a Virtual Organization (VO) with a distinct and separate set of administrative policies (home administration policies plus external resource administrative policies equals the VO [aka your Grid] administrative policies). The context for a Grid 'job execution' is distinguished by the requirements created when operating outside of the home administrative context. Grid technology (aka. middleware) is employed to facilitate formalizing and complying with the Grid context associated with your application execution.

Resource utilization

One characteristic that currently distinguishes Grid computing from distributed computing is the abstraction of a 'distributed resource' into a Grid resource. One result of abstraction is that it allows resource substitution to be more easily accomplished. Some of the overhead associated with this flexibility is reflected in the middleware layer and the temporal latency associated with the access of a Grid (or any distributed) resource. This overhead, especially the temporal latency, must be evaluated in terms of the impact on computational performance when a Grid resource is employed.

Web based resources or Web based resource access is an appealing approach to Grid resource provisioning. A recent GGF Grid middleware evolutionary development 're-factored' the architecture/design of the Grid resource concept to reflect using the W3C WSDL (Web Service Description Language) to implement the concept of a WS-Resource. The stateless nature of the Web, while enhancing the ability to scale, can be a concern for applications that migrate from a stateful resource access context to the Web-based stateless resource access context. The GGF WS-Resource concept includes discussions on accommodating the statelessness associated with Web resources access.

State-of-the-Art 2005

The conceptual framework and ancillary infrastructure are evolving at a fast pace and include international participation. The business sector is actively involved in commercialization of the Grid framework. The 'big science' sector is actively addressing the development environment and resource (aka performance) monitoring aspects. Activity is also observed in providing grid-enabled versions of HPC (High Performance Computing) tools. Activity in the domains of 'little science' appears to be scant at this time. The treatment in the GGF documentation series reflects the HPC roots of the Grid concept framework; this bias should not be interpreted as a restriction in the application of the Grid conceptual framework in its application to other research domains or other computational contexts.

(Theo Wikipedia)