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What Is Grid Computing?

A grid is a collection of computing resources that perform tasks. In its simplest form, a grid appears to users as a large system that provides a single point of access to powerful distributed resources. In its more complex form, which is explained later in this section, a grid can provide many access points to users. In all cases, users treat the grid as a single computational resource. Resource management software such as Sun Grid Engine software accepts jobs submitted by users. The software uses resource management policies to schedule jobs to be run on appropriate systems in the grid. Users can submit millions of jobs at a time without being concerned about where the jobs run.

No two grids are alike. The three key classes of grids, which scale from single systems to supercomputer-class compute farms that use thousands of processors, are as follows:

• Cluster grids are the simplest class. Cluster grids are made up of a set of computer hosts that work together. A cluster grid provides a single point of access to users in a single project or a single department.
• Campus grids enable multiple projects or departments within an organization to share computing resources. Organizations can use campus grids to handle a variety of tasks, from cyclical business processes to rendering, data mining, and more.
• Global grids are a collection of campus grids that cross organizational boundaries to create very large virtual systems. Users have access to compute power that far exceeds resources that are available within their own organization.

The following figure shows the three classes of grids. In the cluster grid, a user's job is handled by only one of the systems within the cluster. However, the user's cluster grid might be part of the more complex campus grid, and the campus grid might be part of the largest global grid. In such cases, the user's job can be handled by any member execution host that is located anywhere in the world.

Sun Grid Engine software provides the power and flexibility required for campus grids. The product is useful for existing cluster grids because it facilitates a smooth transition to creating a campus grid. The Grid Engine system effects this transition by consolidating all existing cluster grids on the campus. In addition, the Grid Engine system is a good start for an enterprise campus that is moving to the grid computing model for the first time.

The Grid Engine software orchestrates the delivery of computational power that is based on enterprise resource policies set by the organization's technical and management staff. The Grid Engine system uses these policies to examine the available computational resources within the campus grid. The system gathers these resources and then allocates and delivers resources automatically, optimizing usage across the campus grid.

To enable cooperation within the campus grid, project owners who use the grid must do the following:

• Negotiate policies
• Develop flexible policies for manual overrides for unique project requirements
• Automatically monitor and enforce the policies

The Grid Engine software can mediate among the entitlements of many departments and projects that are competing for computational resources.