The MOL project: an open, extensible metacomputer

Distributed high-performance computing (so-called metacomputing) refers to the coordinated use of a pool of geographically distributed high-performance computers. The user´s view of an ideal metacomputer is that of a powerful monolithic virtual machine. The implementor´s view, on the other hand, is that of a variety of interacting services implemented in a scalable and extensible manner. We present MOL, the Metacomputer Online environment. In contrast to other metacomputing environments, MOL is not based on specific programming models or tools. It has rather been designed as an open, extensible software system comprising a variety of software modules, each of them specialized in serving one specific task such as resource scheduling, job control, task communication, task migration, user interface, and much more. All of these modules exist and are working. The main challenge in the design of MOL lies in the specification of suitable, generic interfaces for the effective interaction between the modules