Depending on the grid design and its expected use, some of these components may or may not be required, and in some cases they may be combined to form a hybrid component.

8.1. Portal/user interface

Just as a consumer sees the power grid as a receptacle in the wall, a grid user should not see all of the complexities of the computing grid. Although the user interface can come in many forms and be application-specific. A grid portal provides the interface for a user to launch applications that will use the resources and services provided by the grid. From this perspective, the user sees the grid as a virtual computing resource just as the consumer of power sees the receptacle as an. interface to a virtual generator.

Figure 2: Possible user view of a grid

8.2. Security

A major requirement for Grid computing is security. At the base of any grid environment, there must be mechanisms to provide security, including authentication, authorization, data encryption, and so on. The Grid Security Infrastructure (GSI) component of the Globus Toolkit provides robust security mechanisms. The GSI includes an OpenSSL implementation. It also provides a single sign-on mechanism, so that once a user is authenticated, a proxy certificate is created and used when performing actions within the grid. When designing your grid environment, you may use the GSI sign-in to grant access to the portal, or you may have your own security for the portal. The portal will then be responsible for signing in to the grid, either using the user's credentials or using a generic set of credentials for all authorized users of the portal.

Figure 3: Security in a grid environment

8.3. Broker

Once authenticated, the user will be launching an application. Based on the application, and possibly on other parameters provided by the user, the next step is to identify the available and appropriate resources to use within the grid. This task could be carried out by a broker function. Although there is no broker implementation provided by Globus, there is an LDAP-based information service. This service is called the Grid Information Service (GIS), or more commonly the Monitoring and Discovery Service (MDS). This service provides information about the available resources within the grid and their status. A broker service could be developed that utilizes MDS.

Figure 4: Broker service

8.4. Scheduler

Once the resources have been identified, the next logical step is to schedule the individual jobs to run on them. If sets of stand-alone jobs are to be executed with no interdependencies, then a specialized scheduler may not be required. However, if you want to reserve a specific resource or ensure that different jobs within the application run concurrently (for instance, if they require inter-process communication), then a job scheduler should be used to coordinate the execution of the jobs. The Globus Toolkit does not include such a scheduler, but there are several schedulers available that have been tested with and can be used in a Globus grid environment. It should also be noted that there could be different levels of schedulers within a grid environment. For instance, a cluster could be represented as a single resource. The cluster may have its own scheduler to help manage the nodes it contains. A higher-level scheduler (sometimes called a meta scheduler) might be used to schedule work to be done on a cluster, while the cluster's scheduler would handle the actual scheduling of work on the cluster's individual nodes.

Figure 5: Scheduler

8.5. Data management

If any data -- including application modules -- must be moved or made accessible to the nodes where an application's jobs will execute, then there needs to be a secure and reliable method for moving files and data to various nodes within the grid. The Globus Toolkit contains a data management component that provides such services. This component, know as Grid Access to Secondary Storage (GASS), includes facilities such as GridFTP. GridFTP is built on top of the standard FTP protocol, but adds additional functions and utilizes the GSI for user authentication and authorization. Therefore, once a user has an authenticated proxy certificate, he can use the GridFTP facility to move files without having to go through a login process to every node involved. This facility provides third-party file transfer so that one node can initiate a file transfer between two other nodes.

Figure 6: Data management

8.6. Job and resource management

With all the other facilities we have just discussed in place, we now get to the core set of services that help perform actual work in a grid environment. The Grid Resource Allocation Manager (GRAM) provides the services to actually launch a job on a particular resource, check its status, and retrieve its results when it is complete.

Figure 7: Gram

8.7 Job flow in a grid environment

Enabling an application for a grid environment, it is important to keep in mind these components and how they relate and interact with one another. Depending on your grid implementation and application requirements, there are many ways in which these pieces can be put together to create a solution.

9. ADVANTAGES

Grid computing is about getting computers to work together. Almost every organization is sitting on top of enormous, unused computing capacity, widely distributed. Mainframes are idle 40% of the time With Grid computing, businesses can optimize computing and data resources, pool them for large capacity workloads, share them across networks, and enable collaboration. Many consider Grid computing the next logical step in the evolution of the Internet, and maturing standards and a drop in the cost of bandwidth are fueling the momentum we're experiencing today. Virtualization of the computing environment .

10. CHANLLANGES OF GRID

A word of caution should be given to the overly enthusiastic. The grid is not a silver bullet that can take any application and run it a 1000 times faster without the need for buying any more machines or software. Not every application is suitable or enabled for running on a grid. Some kinds of applications simply cannot be parallelized. For others, it can take a large amount of work to modify them to achieve faster throughput. The configuration of a grid can greatly affect the performance, reliability, and security of an organization's computing infrastructure. For all of these reasons, it is important for us to understand how far the grid has evolved today and which features are coming tomorrow or in the distant future

11. CONCLUSION

Grid computing introduces a new concept to IT infrastructures because it supports distributed computing over a network of heterogeneous resources and is enabled by open standards. Grid computing works to optimize underutilized resources, decrease capital expenditures, and reduce the total cost of ownership. This solution extends beyond data processing and into information management as well. Information in this context covers data in databases, files, and storage devices. In this article, we outline potential problems and the means of solving them in a distributed environment. .

12. BIBLIOGRAPHY

[1] www.ibm.com/grid/index.html

[2] Foster, I. and Kesselman, C. (eds) (1999) The Grid: Blueprint for a New Computing Infrastructure.. San Francisco, CA: Morgan Kaufmann

[3] Berman, F., Fox, G. and Hey, T. (2003) Grid Computing: Making the Global Infrastructure a Reality. Chichester: John Wiley & Sons.

[4] Web Site associated with book, Grid Computing: Making the Global Infrastructure a Reality,

http://www.grid2002.org