Francis Vaughan

An examination of operating system support for persistent object systems

Examines operating system support for persistent systems that execute on conventional hardware architectures. The focus of the paper is to examine the inadequacies of traditional operating systems as vehicles for the construction of persistent systems. The authors concentrate on four major areas, namely addressing, stability and resilience, process management and protection. They examine the consequences of making the operating system kernel itself persistent. They conclude by outlining the requirements which must be met by future operating systems designed to support orthogonal persistence.<<ETX>>

Supporting large persistent stores using conventional hardware

Persistent programming systems are generally supported by an object store, a conceptually infinite object repository. Objects in such a repository cannot be directly accessed by user programs; to be manipulated they must be fetched from the object store into virtual memory. Thus in these systems, two different kinds of object addresses may exist: those in the object store and those in virtual memory. The action of changing object store addresses into virtual memory addresses has become known as pointer swizzling and is the subject of this paper. The paper investigates three approaches to pointer swizzling: a typical software address translation scheme, a technique for performing swizzling at page fault time and finally a new hybrid scheme which performs swizzling in two phases. The hybrid scheme supports arbitrarily large pointers and object repositories using conventional hardware. The paper concludes with a comparison of these approaches.

Geographic Information Systems Application on an ATM-based Distributed High Performance Computing System

We present a distributed geographic information system (DGIS) built on a distributed high performance computing environment[1] using a number of software infrastructural building blocks and computational resources interconnected by an ATM-based broadband network. Archiving, access and processing of scientific data are discussed in the context of geographic and environmental applications with special emphasis on the potential for local-area weather, agriculture, soil and land management products. In particular, we discuss the capabilities of a distributed high-performance environment incorporating: high bandwidth communications networks such as Telstras Experimental Broadband Network (EBN)[3]; large capacity hierarchical storage systems; and high performance parallel computing resources.

DISCWorld: A Distributed High Performance Computing Environment

An increasing number of science and engineering applications require distributed and parallel computing resources to satisfy user response-time requirements. Distributed science and engineering applications require a high performance “middleware” which will both allow the embedding of legacy applications as well as enable new distributed programs, and which allows the best use of existing and specialised (parallel) computing resources. We are developing a distributed information systems control environment which will meet the needs of a middleware for scientific applications. We describe our DISCWorld system and some of its key attributes. A critical attribute is architecture scalability. We discuss DISCWorld in the context of some existing middleware systems such as CORBA and other distributed computing research systems such as Legion and Globus. Our approach is to embed applications in the middleware as services, which can be chained together. User interfaces are provided in the form of Java Applets downloadable across the World Wide Web. These form a gateway for user-requests to be transmitted into a semi-opaque “cloud” of high-performance resources for distributed execution.

Protection in Grasshopper: A Persistent Operating System

Persistent systems support a single storage abstraction in which all data may be created and manipulated in a uniform manner, regardless of its longevity. In such systems a protection mechanism is required to ensure that programs can access precisely those objects they are supposed to access and no others. In a monolingual system this protection can be provided by the type system of the programming language; in systems which support multiple persistent languages a separate protection mechanism must be supported. This paper describes the capability- based protection mechanism employed in Grasshopper, a new operating system specifically designed to support persistent systems on a conventional workstation platform. We show that this mechanism provides sufficient power and flexibility to handle a wide variety of protection scenarios.

Geostationary-satellite imagery applications on distributed, high-performance computing

We discuss applications of high resolution geostationary satellite imagery and distributed high performance computing facilities for the storage, processing and delivery of satellite data products. We describe our system which is built on a distributed high performance computing environment using a number of software infrastructural building blocks and computational resources interconnected by an ATM based broadband network. Distributed high performance computing hardware technology underpins our proposed system. In particular we discuss the capabilities of a distributed hardware environment incorporating: high bandwidth communications networks such as Telstras Experimental Broadband Network (EBN); large capacity hierarchical storage systems; and high performance parallel computing resources. We also describe a recent demonstration of our project resources to the remote sensing user community.

An ATM-based Distributed High Performance Computing System

We describe the distributed high performance computing system we have developed to integrate together a heterogeneous set of high performance computers, high capacity storage systems and fast communications hardware. Our system is based upon Asynchronous Transfer Mode (ATM) communications technology and we routinely operate between the geographically distant sites of Adelaide and Canberra (separated by some 1100km) using Telstras ATM-based Experimental Broadband Network (EBN). We discuss some of the latency and performance issues that result from running day-to-day operations across such a long distance network.

Simulation of compression effects during scaleup of a commercial ion-exchange process

A modified version of the general nonlinear multicomponent rate equation chromatography model has been developed to simulate compression effects on system behavior. It accounts for the variations in porosity and particle deformation that occur within a packed bed during compression. This paper investigates the effect of compression on the scaleup of a commercial packed‐bed ion‐exchange process to manufacture a whey growth factor extract (WGFE). The resin employed in the ion‐exchange process is Sepharose Big‐Beads SP (Amrad‐Pharmacia, Sydney, Australia). Compression‐induced changes in packed‐bed porosity and particle diameter for a laboratory‐ (2 cm) and a production‐scale (20 cm) column were estimated from pressure‐drop data by using a modified volume‐averaged continuum theory. These were combined with model parameters from a previous experimental study for two major whey proteins, lactoperoxidase and lactoferrin. Model simulations were performed. First, model parameters were validated by replication of experimental frontal adsorption breakthrough and step‐elution curves. Selection of numerical parameters and accurate adsorption equilibria were identified as critical steps in ensuring successful reconciliation of model predictions with experimental data. The effect of compression on frontal adsorption and elution steps during scaleup was then investigated. For both frontal adsorption and step elution, system behavior was found to be largely independent of compression. Increased compression created only minor and trivial variations in effluent concentration profiles. These were influenced by two competing mechanisms, namely, premature breakthrough and increased external film mass transfer. Further simulations with a smaller particle size and superficial velocity displayed no significant increase in compression effects. Compression effects are not important during scaleup of this system.

Using C as a Compiler Target Language for Native Code Generation in Persistent Systems

Persistent programming languages exhibit several requirements that affect the generation of native code, namely: garbage collection; arbitrary persistence of code, data and processes; dynamic binding; and the introduction of new code into a running system. The problems of garbage collection are not unique to persistent systems and are well understood: both code and data may move during a computation if a compacting collector is employed. However, the problems of garbage collection are exacerbated in persistent systems which must support garbage collection of both RAM resident and disk resident data. Some persistent systems support a single integrated environment in which the compiled code and data is manipulated in a uniform manner, necessitating that compiled code be stored in the object store. Furthermore, some systems assume that the entire state of a running program is resident in a persistent store; in these systems it may be necessary to preserve the state of a program at an arbitrary point in its execution and resume it later. Persistent systems must support some dynamic binding in order to accommodate change. Thus code must be capable of binding to arbitrary data at a variety of times. This introduces the additional complexity that code must be able to call code contained in the persistent store produced by another compilation. In this paper native code generation techniques using C as a target language for persistent languages are presented. The techniques described solve all of the problems described above. They may therefore be applied to any language with these or a subset of these features.

Grasshopper-a persistent operating system for conventional hardware

The paper describes Grasshopper, an operating system designed to provide generic mechanisms capable of being tailored to support a wide range of persistence paradigms. A constraint placed on this design is that the system must be implementable on conventional architectures which support paged virtual memory. The basic system abstractions relating to addressing environments, processes, and protection are described. It is shown that these provide explicit support for distributed persistent objects and processes, stability, and access control. At the same time the system provides the flexibility to allow user implementation of alternative object management techniques.<<ETX>>