Resource Selection and Application Execution in a Grid: A Migration Experience from GT2 to GT4

The latest Globus Toolkit 4 (GT4) version, fully OGSA compliant and almost completely based on Grid Services, is expected to become the reference version of the Globus Toolkit. Therefore, the necessity to migrate from previous versions, especially the widespread GT2, to GT4 is becoming a relevant issue for many Grid systems. We present a migration experience from GT2 to GT4 of a simple tool for resource discovery and selection, and execution of parallel applications in a computational Grid environment. The proposed tool provides a simple and intuitive user interface, a structured view of Grid resources, a simple mechanism for resource selection, and support for application staging and execution. We discuss some relevant differences between GT2 and GT4, particularly for the Monitoring and Discovering subsystem. GT4 turns out to be more powerful and flexible. Just because we address the implementation of basic functionalities, the proposed discussion may be of general interest.