The core Legion object model

The Legion project at the University of Virginia is an architecture for designing and building system services that provide the illusion of a single virtual machine to users, a virtual machine that provides secure shared object and shared name spaces, application adjustable fault tolerance, improved response time, and greater throughput. Legion targets wide area assemblies of workstations, supercomputers, and parallel supercomputers. Legion tackles problems not solved by existing workstation based parallel processing tools; the system will enable fault tolerance, wide area parallel processing, interoperability, heterogeneity, a single global name space, protection, security, efficient scheduling, and comprehensive resource management. The paper describes the core Legion object model, which specifies the composition and functionality of Legion's core objects-those objects that cooperate to create, locate, manage, and remove objects in the Legion system. The object model facilitates a flexible extensible implementation, provides a single global name space, grants site autonomy to participating organizations, and scales to millions of sites and trillions of objects.