Over the last decade, the Grid community has begun to converge on a layered model that allows development of the complex system of services and software required to integrate Grid resources. The Community Grid Model (a layered abstraction of the grid) being developed in a loosely coordinated manner throughout academia and the commercial sector.

The bottom horizontal layer of the Community Grid Model consists of the hardware resources that underlie the Grid. Such resources include computers, networks, data archives, instruments, visualization devices and so on. Moreover, the resource pool represented by this layer is highly dynamic, both as a result of new resources being added to the mix and old resources being retired, and as a result of varying observable performance of the resources in the shared, multi-user environment of the Grid.

Figure 1: Layered architecture of the Community Grid Model.

The next horizontal layer (common infrastructure) consists of the software services and systems, which virtualized the Grid. The key concept at the common infrastructure layer is community agreement on software, which will represent the Grid as a unified virtual platform and provide the target for more focused software and applications.

The next horizontal layer (user and application-focused Grid middleware, tools and services) contains software packages built atop the common infrastructure. This software serves to enable applications to more productively use Grid resources by masking some of the complexity involved in system activities such as authentication, file transfer.

6. TYPES OF GRID

Grid computing can be used in a variety of ways to address various kinds of application requirements. Often, grids are categorized by the type of solutions that they best address. The three primary types of grids are

Computational grid

A computational grid is focused on setting aside resources specifically for computing power. In this type of grid, most of the machines are high-performance servers.

Scavenging grid
A scavenging grid is most commonly used with large numbers of desktop machines. Machines are scavenged for available CPU cycles and other resources. Owners of the desktop machines are usually given control over when their resources are available to participate in the grid.

Data grid

A data grid is responsible for housing and providing access to data across multiple organizations. Users are not concerned with where this data is located as long as they have access to the data. For example, you may have two universities doing life science research, each with unique data. A data grid would allow them to share their data, manage the data, and manage security issues such as who has access to what data.

Another common distributed computing model that is often associated with or confused with Grid computing is peer-to-peer computing. In fact, some consider this is another form of Grid computing.

7. THE KIND OF GRID TOOLS

Infrastructure components include file systems, schedulers and resource managers, messaging systems, security applications, certificate authorities, and file transfer mechanisms like Grid FTP.

• Directory services. Systems on a grid must be capable of discovering what services are available to them. In short, Grid systems must be able to define (and monitor) a grid’s topology in order to share and collaborate. Many Grid directory services implementations are based on past successful models, such as LDAP, DNS, network management protocols, and indexing services.
• Schedulers and load balancers. One of the main benefits of a grid is maximizing efficiency. Schedulers and load balancers provide this function and more. Schedulers ensure that jobs are completed in some order (priority, deadline, urgency, for instance) and load balancers distribute tasks and data management across systems to decrease the chance of bottlenecks.
• Developer tools. Every arena of computing endeavor requires tools that allow developers to succeed. Tools for grid developers focus on different niches (file transfer, communications, environment control), and range from utilities to full-blown APIs.
• Security. Security in a grid environment can mean authentication and authorization -- in other words, controlling who/what can access a grid’s resources -- but it can mean a lot more. For instance, message integrity and message confidentiality are crucial to financial and healthcare environments