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|style="background:#DFFFFF;width:500px;"|'''Near final draft of Lead/Introduction'''<br /> [[User:JLSjr|JLSjr]] ([[User talk:JLSjr|talk]]) 09:56, 14 April 2010 (UTC)
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A '''Distributed operating system''' is the logical cumulative aggregation of operating system software
The first is a minimal, low-level, node-servicing kernel, situated directly above the bare-metal of a node’s hardware. The kernel provides the foundation for all node-level activities. The second is a higher-level collection of system-servicing management components and services, the System Management Servers. This collection of globally-connected management components exists immediately above the microkernel, and below any user applications or APIs that might reside at higher levels.<ref>Distributed Operating Systems: The Logical Design, 1st edition Goscinski, A. 1991 Distributed Operating Systems: the Logical Design. 1st. Addison-Wesley Longman Publishing Co., Inc.</ref> These two entities, the kernel and the management components collection, work together in supporting the distributed operating system’s goal of seamlessly integrating all network-connected resources and functionality into an efficient, accessible, and unified system.<ref>Design of Distributed Operating Systems: Concepts and Technology Fortier, P. J. 1986 Design of Distributed Operating Systems: Concepts and Technology. Intertext Publications, Inc.,/McGraw-Hill, Inc.</ref>
== Overview ==
=== The Kernel ===
The Kernel is a minimal, but complete set of node-level utilities necessary for access to a node’s underlying hardware and resources. These mechanisms provide the complete set of “building-blocks” essential for node operation; mainly low-level allocation, management, and disposition of a node’s resources, processes, communication, and I/O management support functions. These functions are made possible by exposing a concise, yet comprehensive array of primitive mechanisms and services. The kernel is arguably the primary consideration in a distributed operating system; however, within the kernel, the subject of foremost importance is that of a well-structured and highly-efficient communications sub-system.<ref>Distributed Operating Systems: The Logical Design, 1st edition Goscinski, A. 1991 Distributed Operating Systems: the Logical Design. 1st. Addison-Wesley Longman Publishing Co., Inc.</ref>
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In a distributed operating system, the kernel is often defined by a relative to absolute minimal architecture. A Kernel of this design is referred to as a Microkernel.<ref>Using LOTOS for specifying the CHORUS distributed operating system kernel Pecheur, C. 1992. Using LOTOS for specifying the CHORUS distributed operating system kernel. Comput. Commun. 15, 2 (Mar. 1992), 93-102.</ref> <ref>COOL: kernel support for object-oriented environments
Habert, S. and Mosseri, L. 1990. COOL: kernel support for object-oriented environments. In Proceedings of the European Conference on Object-Oriented Programming on Object-Oriented Programming Systems, Languages, and Applications (Ottawa, Canada). OOPSLA/ECOOP '90. ACM, New York, NY, 269-275.</ref> The microkernel usually contains only mechanisms and services which would, if otherwise removed, render a node or the global system functionally incapable. The minimal nature of the microkernel strongly enhances a distributed operating system’s modular potential.<ref>Distributed Operating Systems: Concepts and Design
Sinha, P. K. 1996 Distributed Operating Systems: Concepts and Design. 1st. Wiley-IEEE Press.</ref> It is generally the case that the kernel is implemented directly on the bare metal of a node’s hardware; it is also common for a kernel to be replicated over all nodes.<ref>Distributed Operating Systems
Galli, D. L. 1999 Distributed Operating Systems: Concepts and Practice. 1st. Prentice Hall PTR.</ref>
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A well-devised minimal microkernel of functionally-cohesive modular architecture can exhibit an advanced level of flexibility in adapting to heterogeneous hardware, and in supporting different organizational paradigms in higher-level structures; all from a single replicated entity. This ubiquitous quality of a system’s kernel also supports much greater system-level flexibility and scalability. The combination of a kernel’s minimal design and ubiquitous coverage greatly aids in global system extensibility, and the ability to dynamically introduce new nodes or services.<ref>Distributed Operating Systems and Algorithms Chow, R. and Chow, Y. 1997 Distributed Operating Systems and Algorithms. Addison-Wesley Longman Publishing Co., Inc.</ref>
=== System Management Components ===
The logical price of realizing a distributed system – including its operating system – must be calculated in terms of overcoming vast amounts of complexity on many levels, and in many areas. This calculation includes the depth, breadth, and range of design investment and architectural planning required in achieving even modest levels of success. These development considerations are critical and unforgiving, as the overwhelming majority of a distributed system’s details require an inordinate completeness of understanding from the start. As an aid in this effort, most rely strongly on the immense amount of documented experience and research accomplished towards distributed computing which exists, and continues today.▼
A node’s management server collection is defined by the composite of a node’s system software not directly required within the kernel, which support the node’s responsibilities to the overall system. These responsibilities focus principally on transparency or the “system image”; and subsequently on achieving the global system goals of efficiency, flexibility, consistency, and reliability. Transparency, with respect to the traditional operating system is the abstraction of difficult or tedious aspect of a system into a more acceptable or desirable quality.
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In a distributed system, the exceptional degree of inherent complexity could easily render the system and its operating system an anathema to any user. As a result, transparency is a critical point of focus in most, if not all areas of the system; namely with respect to performance, failure, access, migration, concurrency, and ___location to mention just a few. Quite often, an effort to realize success in any particular area illuminates conflict with efforts in others. Therefore, a consistent and balanced perspective and understanding of the overall system can help identify points of the diminishing returns quickly.
Many notable experts look to the early 1970s for the earliest distributed systems, complete by definition and capable of being considered wholly. Research and experimentation efforts began in earnest in the mid to late-1970s and continued into the early 1990s, with some implementations achieving modest commercial success. The subject of distributed systems however, has a much richer historical perspective when considering severally some of the individual primordial strides towards distributed computing. There are several instances of fundamental and pioneering implementations of primitive distributed systems and component concepts dating back to the early 1950s. Looking to the modern distributed system and its future, the accelerating proliferation of multiprocessor systems and multi-core processors has led to a re-emergence of the distributed system concept. The inherent challenges in many-core and multiprocessor science has led to an enormous increase in distributed system related research. Many of these research efforts investigate and describe plausible paradigms for the future of distributed computing.▼
=== Together as an Operating System ===
The architecture and design of a distributed operating system is specifically aligned with realizing these goals and transparencies in an attempt to protect the user from the issues arising from the system’s physically separated state. Simply said, a distributed operating system attempts to provide a highly efficient and reliable computing framework with a minimum user awareness of the underlying command and control efforts. The multi-level collaboration between a kernel and management components, and in turn between distinct nodes in a distributed system is the key functional space of the distributed operating system. However, this opportunity comes at a very high price.
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▲The logical price of realizing a distributed system – including its operating system – must be calculated in terms of overcoming vast amounts of complexity on many levels, and in many areas. This calculation includes the depth, breadth, and range of design investment and architectural planning required in achieving even modest levels of success.
▲Many notable experts look to the early 1970s for the earliest distributed systems, complete by definition and capable of being considered and implemented wholly. Research and experimentation efforts began in earnest in the mid to late-1970s and continued into the early 1990s, with
== Description ==
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