Snowflake: Spanning administrative domains

Many distributed systems provide a ``single-system image\u27\u27 to their users, so the user has the illusion that they are using a single system when in fact they are using many distributed resources. It is a powerful abstraction that helps users to manage the complexity of using distributed resources. The goal of the Snowflake project is to discover how single-system images can be made to span administrative domains. Our current prototype organizes resources in namespaces and distributes them using Java Remote Method Invocation. Challenging issues include how much flexibility should be built into the namespace interface, and how transparent the network and persistent storage should be. We outline future work on making Snowflake administrator-friendly

Issues in Extensible Operating Systems

Operating systems research has traditionally consisted of adding functionality to the operating system or inventing and evaluating new methods for performing functions. Regardless of the research goal, the single constant has been that the size and complexity of operating systems increase over time. As a result, operating systems are usually the single most complex piece of software in a computer system, containing hundreds of thousands, if not millions, of lines of code. Today’s operating system research is directed at finding new ways to structure the operating system in order to increase its flexibility, allowing it to adapt to changes in the application set it must support. This paper discusses the issues involved in designing such extensible systems and the array of choices facing the operating system designer. We present a framework for describing extensible operating systems and then relate current operating systems to this framework.Engineering and Applied Science

Effective information sharing using update logs

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (leaves 80-88).by James William O'Toole, Jr.Ph.D

Naming and sharing resources across administrative boundaries

I tackle the problem of naming and sharing resources across administrative boundaries. Conventional systems manifest the hierarchy of typical administrative structure in the structure of their own mechanism. While natural for communication that follows hierarchical patterns, such systems interfere with naming and sharing that cross administrative boundaries, and therefore cause headaches for both users and administrators. I propose to organize resource naming and security, not around administrative domains, but around the sharing patterns of users. The dissertation is organized into four main parts. First, I discuss the challenges and tradeoffs involved in naming resources and consider a variety of existing approaches to naming. Second, I consider the architectural requirements for user-centric sharing. I evaluate existing systems with respect to these requirements. Third, to support the sharing architecture, I develop a formal logic of sharing that captures the notion of restricted delegation. Restricted delegation ensures that users can use the same mechanisms to share resources consistently, regardless of the origin of the resource, or with whom the user wishes to share the resource next. A formal semantics gives unambiguous meaning to the logic. I apply the formalism to the Simple Public Key Infrastructure and discuss how the formalism either supports or discourages potential extensions to such a system. Finally, I use the formalism to drive a user-centric sharing implementation for distributed systems. I show how this implementation enables end-to-end authorization, a feature that makes heterogeneous distributed systems more secure and easier to audit. Conventionally, gateway services that bridge administrative domains, add abstraction, or translate protocols typically impede the flow of authorization information from client to server. In contrast, end-to-end authorization enables us to build gateway services that preserve authorization information, hence we reduce the size of the trusted computing base and enable more effective auditing. I demonstrate my implementation and show how it enables end-to-end authorization across various boundaries. I measure my implementation and argue that its performance tracks that of similar authorization mechanisms without end-to-end structure. I conclude that my user-centric philosophy of naming and sharing benefits both users and administrators

A File System Component Compiler

File System development is a difficult and time consuming task, the results of which are rarely portable across operating systems. Several proposals to improve the vnode interface to allow for more flexible file system design and implementation have been made in recent years, but none is used in practice because they require costly fundamental changes to kernel interfaces, only operating systems vendors can make those changes, are still non-portable, tend to degrade performance, and do not appear to provide immediate return on such an investment. This proposal advocates a language for describing file systems, called FiST. The associated translator can generate portable C code — kernel resident or not — that implements the described file system. No kernel source code is needed and no existing vnode interface must change. The performance of the file systems automatically generated by FiST can be within a few percent of comparable hand-written file systems. The main benefits to automation are that development and maintenance costs are greatly reduced, and that it becomes practical to prototype, implement, test, debug, and compose a vastly larger set of such file systems with different properties. The proposed thesis will describe the language and its translator, use it to implement a few file systems on more than one platform, and evaluate the performance of the automatically generated code

Mikropalvelut kameroilla ja kuvavertailulla

This thesis was about implementations of Microservices that uses cameras and image comparison to verify a situation visually. The solution was done in ad-hoc fashion utilizing existing command-line tooling and it was controlled by dynamic scripting language with managed runtime. The purpose of the original service was to observe quite drastic changes between images taken from the same situation. This thesis walks through the old solution from its key concepts offering a baseline for the new solution. After that the new solution is examined from the same key functionality point of view together with some implementation technical notes. The problems that came up during the development and testing phases are looked with the solutions tired and selected together with some documentation about the imaging libraries used. Some core differences between the old and new solutions are examined by measurements and observations. Both of the solutions are used in different environment at the moment. They both expose the same functional interface so replacing the other is possible. Even though the old solution performs well in its current tasks replacing it with the modern one might give that environment more flexibility to extend is test scenario capability

Mikropalvelut kameroilla ja kuvavertailulla

This thesis was about implementations of Microservices that uses cameras and image comparison to verify a situation visually. The solution was done in ad-hoc fashion utilizing existing command-line tooling and it was controlled by dynamic scripting language with managed runtime. The purpose of the original service was to observe quite drastic changes between images taken from the same situation. This thesis walks through the old solution from its key concepts offering a baseline for the new solution. After that the new solution is examined from the same key functionality point of view together with some implementation technical notes. The problems that came up during the development and testing phases are looked with the solutions tired and selected together with some documentation about the imaging libraries used. Some core differences between the old and new solutions are examined by measurements and observations. Both of the solutions are used in different environment at the moment. They both expose the same functional interface so replacing the other is possible. Even though the old solution performs well in its current tasks replacing it with the modern one might give that environment more flexibility to extend is test scenario capability

Software implemented fault tolerance for microprocessor controllers: fault tolerance for microprocessor controllers

It is generally accepted that transient faults are a major cause of failure in micro processor systems. Industrial controllers with embedded microprocessors are particularly at risk from this type of failure because their working environments are prone to transient disturbances which can generate transient faults. In order to improve the reliability of processor systems for industrial applications within a limited budget, fault tolerant techniques for uniprocessors are implemented. These techniques aim to identify characteristics of processor operation which are attributed to erroneous behaviour. Once detection is achieved, a programme of restoration activity can be initiated. This thesis initially develops a previous model of erroneous microprocessor behaviour from which characteristics particular to mal-operation are identified. A new technique is proposed, based on software implemented fault tolerance which, by recognizing a particular behavioural characteristic, facilitates the self-detection of erroneous execution. The technique involves inserting detection mechanisms into the target software. This can be quite a complex process and so a prototype software tool called Post-programming Automated Recovery UTility (PARUT) is developed to automate the technique's application. The utility can be used to apply the proposed behavioural fault tolerant technique for a selection of target processors. Fault injection and emulation experiments assess the effectiveness of the proposed fault tolerant technique for three application programs implemented on an 8, 16, and 32- bit processors respectively. The modified application programs are shown to have an improved detection capability and hence reliability when the proposed fault tolerant technique is applied. General assessment of the technique cannot be made, however, because its effectiveness is application specific. The thesis concludes by considering methods of generating non-hazardous application programs at the compilation stage, and design features for incorporation into the architecture of a microprocessor which inherently reduce the hazard, and increase the detection capability of the target software. Particular suggestions are made to add a 'PARUT' phase to the translation process, and to orientate microprocessor design towards the instruction opcode map