Introduction to XtremWeb

XtremWeb is a research project belonging to light-weight Grids. It's an Open Source platform designed to help you to build your own Grid based on Deskop PC, in your University, your Enterprise or from volunteer PC on Internet. Our motivation for developping XtremWeb is to explore scientific issues and applications of Desktop Grid, Global Computing and Peer to Peer distributed systems.

Like the other Large Scale Distributed Systems, an XW platform uses a) remote resources (PCs, workstations, servers) connected to Internet or b) a pool of resources (PCs, workstations, servers) inside a LAN. Participants of an XW platform cooperate by providing their CPU idle time.

XtremWeb is composed of Client, Coordinator and Workers. This architecture corresponds to most of well known Global Computing Projects. During the execution, the workers contact the Server to get jobs. In response, the Server send a set of parameter and it also may send an application if the application is not already stored in the Workers. When the Workers have finished to compute their job, they contact the Coordinator to send the results. Depending on the result size, the communication between the Workers and the Result collector use different protocols. Currently, the worker may send result size up to 100 MBytes. In this architecture, the Client and the Server are the same computer.

XtremWeb can also be used to build centralized Peer-to-Peer Systems such as some well known projects related to audio file exchange. However, currently, XtremWeb doesn't allow to store data on the Client/Worker resources. XtremWeb only allows P2P computing using the following design:

Typically, one or several applications are downloaded on the Workers. Any Worker may submit jobs by contacting the P2P Server. In this case, the Worker behaves as a Client. Jobs submitted by Client are registered on the Server and scheduled on Workers. In this architecture any Worker can be a Client. Currently we recommend to use only trusted applications with this architecture. The next release of XW will encompass a sandboxing mechanism to protect the Worker of hackers attack. With this mechanism, any program may be submitted to the system and ran on a protected Worker.

Note that the XtremWeb is not limited to centralized architectures and we are currently extending it to a hierarchical design. Also, Workers may send their results directly to Clients to limit the bandwidth consummation.