  The availability of powerful microprocessors and high-speed networks as
commodity components has enabled high performance computing on distributed
systems (wide-area cluster computing). In this environment, as the resources
are usually distributed geographically at various levels (department,
enterprise, or worldwide) there is a great challenge in integrating,
coordinating and presenting them as a single resource to the user; thus forming
a computational grid. Another challenge comes from the distributed ownership of
resources with each resource having its own access policy, cost, and mechanism.
  The proposed Nimrod/G grid-enabled resource management and scheduling system
builds on our earlier work on Nimrod and follows a modular and component-based
architecture enabling extensibility, portability, ease of development, and
interoperability of independently developed components. It uses the Globus
toolkit services and can be easily extended to operate with any other emerging
grid middleware services. It focuses on the management and scheduling of
computations over dynamic resources scattered geographically across the
Internet at department, enterprise, or global level with particular emphasis on
developing scheduling schemes based on the concept of computational economy for
a real test bed, namely, the Globus testbed (GUSTO).
