Legion was the first integrated grid middleware architected from first principles to address the complexity of grid environments. Just as a traditional operating system provides an abstract interface to the underlying physical resources of a machine, Legion was designed to provide a powerful virtual machine interface layered over the distributed, heterogeneous, autonomous, and fault-prone physical and logical resources that constitute a grid. We believe that without a solid, integrated, operating system-like grid middleware, grids will fail to cross the chasm from bleeding-edge supercomputing users to more mainstream computing. This work provides an overview of the architectural principles that drove Legion, a high-level description of the system with complete references to more detailed explanations, and the history of Legion from first inception in August 1993 through commercialization. We present a number of important lessons, both technical and sociological, learned during the course of developing and deploying Legion.

Abstract One benefit of a computational Grid is the ability to run high‐performance applications over distributed resources simply and securely. We demonstrated this benefit with an experiment in which we studied the protein‐folding process with the CHARMM molecular simulation package over a Grid managed by Legion, a Grid operating system. High‐performance applications can take advantage of Grid resources if the Grid operating system provides both low‐level functionality as well as high‐level services. We describe the nature of services provided by Legion for high‐performance applications. Our experiences indicate that human factors continue to play a crucial role in the configuration of Grid resources, underlying resources can be problematic, Grid services must tolerate underlying problems or inform the user, and high‐level services must continue to evolve to meet user requirements. Our experiment not only helped a scientist perform an important study, but also showed the viability of an integrated approach such as Legion's for managing a Grid. Copyright © 2004 John Wiley & Sons, Ltd.

Abstract The Legion Grid Portal is an interface to a Grid system. Users interact with the portal, and hence a Grid, through an intuitive interfacefrom which they can view files, submit and monitor runs, and view accounting information. The architecture of the portal is designed to accommodate multiple diverse Grid infrastructures, legacy systems, and application‐specific interfaces. The current implementation of the Legion Grid Portal is with familiar Web technologies over the Legion Grid infrastructure. The portal can be extended in a number of directions—additional support for Grid administrators, greater number of application‐specific interfaces, interoperability between Grid infrastructures, and interfaces for programming support. The portal has been in operation since February 2000 on npacinet, a worldwide Grid managed byLegion on NPACI resources. Copyright © 2002 John Wiley & Sons, Ltd.

One benefit of a computational grid is the ability to run high-performance applications over distributed resources simply and securely. We demonstrate this benefit with an experiment in which we studied the protein folding process with the CHARMM molecular simulation package over a grid managed by Legion, a grid operating system. High-performance applications can take advantage of grid resources if the grid operating system provides both low level functionality as well as high-level services. We describe the nature of services provided by Legion for high-performance applications. Our experiences indicate that human factors continue to play a crucial role in the configuration of grid resources, underlying resources can be problematic, grid services must tolerate underlying problems or inform the user, and high-level services must continue to evolve to meet user requirements. Our experiment not only helped a scientist perform an important study, but also showed the viability of an integrated approach such as Legion's for managing a grid.