Legion: The Next Logical Step Toward a Worldwide Virtual Computer

Andrew S. Grimshaw, William A. Wulf, James C. French, Alfred C. Weaver, Paul F. Reynolds Jr., Legion: The Next Logical Step Toward a Nationwide Virtual Computer, June 08, 1994.

Andrew S. Grimshaw, William A. Wulf, James C. French, Alfred C. Weaver, Paul F. Reynolds Jr., A Synopsis of the Legion Project, June 08, 1994.

Andrew S. Grimshaw, Anh Nguyen-Tuong, William A. Wulf, Campus-Wide Computing: Early Results Using Legion at The University of Virginia, March 27, 1995.
Abstract: The Legion project at the University of Virginia is an attempt to provide system services that provide the illusion of a single virtual machine to users, a virtual machine that provides both improved response time via parallel execution and greater throughput. Legion is targeted towards both workstation clusters and towards larger, wide-area, assemblies of workstations, supercomputers, and parallel supercomputers. Rather than construct Legion from scratch we are extending an existing object-oriented parallel processing system by aggressively incorporating lessons learned over twenty years by the heterogeneous distributed systems community. The campus-wide virtual computer is an early Legion prototype. In this paper we present challenges that had to be overcome to realize a working CWVC, as well as performance on a production biochemistry application.

Mike Lewis, Andrew Grimshaw, The Core Legion Object Model, August 1995.
Abstract: This document describes the core Legion object model. The model specifies the composition and functionality of Legion's core objects - those objects that cooperate to create, locate, manage, and remove objects from the Legion system. The model reflects the underlying philosophy and objectives of the Legion project. In particular, the object model facilitates a flexible extensible implementation, provides a single persistent name space, grants site autonomy to participating organizations, and scales to millions of sites and trillions of objects. Further, it offers a framework that is well suited to providing mechanisms for high performance, security, fault tolerance, and commerce.

William A. Wulf, Chenxi Wang, Darrell Kienzle , A New Model of Security for Distributed Systems , August 10, 1995 .
Abstract: With the rapid growth of the information age, electronic activities of many kinds are becoming more common. The need for protection and security in this environment has never been greater. The conventional approach to security has been to enforce a system-wide policy, but this approach will not work for large distributed systems where entirely new security issues and concerns are emerging.We argue that a new model is needed that shifts the emphasis from "system as enforcer" to user-definable policies in which the cost scales with the degree of security required. Users ought to be able to select the level of security they need and pay only the overhead necessary to achieve it. Moreover, ultimately, they must be responsible for their own security. This research is being carried out in the context of the Legion project. We start by describing the objectives and philosophy of the overall project and then present our conceptual model and tentative implementation plan. A set of technical challenges is also addressed.

Andrew S. Grimshaw, Jon B. Weissman, Emily A. West, Ed Loyot, Jr., MetaSystems: An Approach Combining Parallel Processing and Heterogeneous Distributed Computing Systems, December 29, 1992.
Abstract: Large metasystems comprised of a variety of interconnected high-performance architectures are becoming available to researchers. To fully exploit these new systems, software must be provided that is easy to use, supports large degrees of parallelism in applications code, and manages the complexity of the underlying physical architecture for the user. This paper describes our approach to constructing and exploiting metasystems. Our approach inherits features of earlier work on parallel processing systems and heterogeneous distributed computing systems. In particular, we build on Mentat, an object-oriented parallel processing system developed at the University of Virginia that provides large amounts of easy-to-use parallelism for MIMD architectures.

Roger R. Harper, Interoperability of Parallel Systems: Running PVM Applications in the Legion Environment, May 3, 1995.
Abstract: Parallel Programming systems based on loosely coupled networks of computers are becoming more and more popular. One of the more popular systems is Parallel Virtual Machine (PVM) which allows a user to think of a set of computers as a single parallel machine. The Legion project at the University of Virginia is another attempt to provide users with the illusion that a collection of computers is a single virtual machine. This report describes a software library that allows applications written for the PVM system to run in the Legion Environment. The report describes the design and development of the library, and compares the performance of the library, and PVM, on established benchmark applications.

To view the Legion Web Page click here.

[Overview] [Documnetation] [Mentat Team] [Distribution] [Sample Programs] [Slides] [New Features]

If you have any questions about Mentat please feel free to e-mail us at mentat@virginia.edu, Department of Computer Science, Thornton Hall, University of Virginia, Charlottesville, Virginia 22903.