Resource management in the Cronus distributed operating system

Abstract

Cronus [l-7] is an object oriented distibuted system which operates in a heterogeneous computer environment of interconnected local area networks. As a distributed system architecture, Cronus faces a number of resource management issues not present in non-distributed architectures. Stmtegies for effectively conuolling the redundancy and reconfigurability inherent in Cronus are needed to take advantage of the distributed system environment. These strategies for resource management are often conveniently separated into policies and mechanisms. A policy is a goal or guideline set by a system administrator or component designer constraining the decisions made by a resource allocator. A mechanism is an internal system structure designed to implement a class of policies.In the Cronus distributed system model, there are currently two general aspects of resource allocation mechanisms which are particular to the network environment and must be effectively managed. One of these is the binding of a client request to a pticular resource manager for those resources which are available redundantly. Redundancy comes in two forms: replicated objects, (e.g., a mu&copy file) and replicated managers (any manager for a type can create a new instance of that object type). For both forms the selection of an object manager to provide the given service is an important resource management policy decision. The other important aspect of resource management mechanism is the ability to reconfigure parts of the system by dynamically migrating objects. Object migration is a powerful tool &or matching system resources to tasks in a manner that attempts to maximize some measure of system performance, reliability, or survivability, Both static reconfiguration (e.g., choosing or amending the placement of object managers and their associated objects), and dynamic recontiguration (e.g., movmg an individual object in direct response to demand for its use possible in the Cronus architecture and design.Cmnus development has been suppoltcd by the Rome Air Dwelopment Center, under contracts F30602-81-C-0132 and F30602.84-C-0171,The general approach to resource management in Cronus is to individually control the management of the classes of objects which make up the system. This approach extends Cronus resource management concepts beyond system resources to the abstract resources developed by applications. Resource management for an individual abstract resource (type) and for groups of related resource types (services) in G-onus is based on combining a number of carefully planned mechanisms which are part of the system architecture. In addition to resource management by resource type, a client specific policy which considers collections of object types used in a specific context can be constructed.In Cronus we achieve system wide and easily controllable resource management by requiring the object managers to cooperate in enforcing a resource management policy for their resource type. An object manager can redirect operations to a peer manager on another ...

The C(2) System Internet Experiment. Volume 1

“…A discussion of how the object model was applied to the Cronus DOS Architectur'e can be found in [Schantz86]. The model proved qIte effective in organizing the types of resources commonly found in traditional operating systems, including processes, directories, files, users and groups; and for extending support for these resources through a distributed collection of heterogeneous host systems, providing controlled remote resource access, survivable operation, scalability, and resource management.…”

Cognitive Radio Sensor Networks in Smart Grid

“…Indeed, important aspects of it were developed in large part under the umbrella of the US military, due to its extensive operational needs, e.g. the Cronus project [16]. Middleware provides higher-level and network-centric building blocks (abstractions such as distributed objects, distributed tuples, remotely updated variables, etc) than an operating system provides, and more suitable to distributed computing.…”

Adaptive and Reflective Middleware for Distributed Real-Time and Embedded Systems

“…• Years of research, iteration, refinement, and successful use -The use of middleware and DOC middleware is not new [Sch86]. Middleware concepts emerged alongside experimentation with the early Internet (and even its predecessor ARPAnet), and DOC middleware systems have been continuously operational since the mid 1980's.…”