Diskless supercomputers: Scalable, reliable I/O for the Tera-Op technology base

Computing is seeing an unprecedented improvement in performance; over the last five years there has been an order-of-magnitude improvement in the speeds of workstation CPU's. At least another order of magnitude seems likely in the next five years, to machines with 500 MIPS or more. The goal of the ARPA Teraop program is to realize even larger, more powerful machines, executing as many as a trillion operations per second. Unfortunately, we have seen no comparable breakthroughs in I/O performance; the speeds of I/O devices and the hardware and software architectures for managing them have not changed substantially in many years. We have completed a program of research to demonstrate hardware and software I/O architectures capable of supporting the kinds of internetworked 'visualization' workstations and supercomputers that will appear in the mid 1990s. The project had three overall goals: high performance, high reliability, and scalable, multipurpose system

Asynchronous replication of metadata across multi-master servers in distributed data storage systems

In recent years, scientific applications have become increasingly data intensive. The increase in the size of data generated by scientific applications necessitates collaboration and sharing data among the nation\u27s education and research institutions. To address this, distributed storage systems spanning multiple institutions over wide area networks have been developed. One of the important features of distributed storage systems is providing global unified name space across all participating institutions, which enables easy data sharing without the knowledge of actual physical location of data. This feature depends on the ``location metadata\u27\u27 of all data sets in the system being available to all participating institutions. This introduces new challenges. In this thesis, we study different metadata server layouts in terms of high availability, scalability and performance. A central metadata server is a single point of failure leading to low availability. Ensuring high availability requires replication of metadata servers. A synchronously replicated metadata servers layout introduces synchronization overhead which degrades the performance of data operations. We propose an asynchronously replicated multi-master metadata servers layout which ensures high availability, scalability and provides better performance. We discuss the implications of asynchronously replicated multi-master metadata servers on metadata consistency and conflict resolution. Further, we design and implement our own asynchronous multi-master replication tool, deploy it in the state-wide distributed data storage system called PetaShare, and compare performance of all three metadata server layouts: central metadata server, synchronously replicated multi-master metadata servers and asynchronously replicated multi-master metadata servers

A Java based internet file system service

As the Internet grows and users become more mobile, they will need to be able to access from remote locations all of the same things that they use in their offices. Some users accomplish this by taking everything with them, in the form of high-priced, high-powered laptop computers. Another solution is to use Internet-based services to deliver all of these same things to the user. This thesis and its related project address a Java-based File System Service that uses a combination of local and remote servers, as well as LANs and WANs (including the Internet) to provide users with access to their files regardless of where the user logs in; across the room, across town, across the country or around the world. In the process, this thesis will explore many topics related to wide area file system design including transport issues, file and directory caching, authentication and authorization

Um modelo distribuído de armazenamento hierárquico de conhecimento médico

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia e Gestão do Conhecimento, Florianópolis, 2013.O advento da disseminação e consolidação dos sistemas computacionais, como ferramentas de apoio aos mais variados tipos de negócios, criou uma dependência dos usuários em geral, em armazenar mais e mais seus dados. Atualmente é inquestionável a necessidade de registros anteriores de transações dos usuários em sistemas operacionais. Esta necessidade vai, por exemplo, desde a recuperação de um e-mail de anos anteriores, passando por registros de transações bancárias legadas, indo até prontuários eletrônicos. Com esta crescente demanda de armazenamento de dados, informações e conhecimento, para os mais variados nichos da Indústria e da Ciência em geral, criou um interessante espaço para pesquisa e desenvolvimento de formas alternativas para a persistência de longo prazo em sistemas computacionais. Na área médica, esta premissa é ainda mais verdadeira, pois todos os dias, centenas de milhares de pacientes ao redor do mundo, realizam exames médicos baseados em imagens, buscando auxílio para o diagnóstico dos mais variados tipos de doenças. As formas de persistência de dados que atualmente são utilizadas na área médica, em sua grande maioria, se apoiam no paradigma relacional, que geralmente suportam os sistemas de informação ou conhecimento que estão nos hospitais e clínicas médicas. Neste sentido, esta tese propôs um novo modelo de armazenamento para sistemas médicos baseados em imagens. Este modelo foi concebido a partir de um paradigma hierárquico, seguindo o padrão para imagens médicas internacionalmente reconhecido (DICOM), o que além de representar os dados de uma forma mais natural, simplifica o processo de busca e recuperação. Ao final dos experimentos e das etapas de análises dos resultados, o modelo proposto mostrou ter um desempenho mais eficiente no geral, se comparado ao modelo atual, utilizando bancos de dados relacionais.Abstract : The advent of the spread and consolidation of computer systems as tools supporting various kinds of business, created a dependence on general users to store more and more data. Currently there is an unquestionable need for previous records of user transactions in computer systems. This will need, for example, from the restore of an e-mail in previous years, going through records of bank transactions legacy, going to electronic records. With this increasing demand for data storage, information and knowledge for various niches of Science and Industry in general has created an interesting space for research and development of alternative forms for the persistence of long-term computer systems. In the medical field, this premise is even more true because every day, hundreds of thousands of patients around the world, conduct medical examinations based on images, seeking aid for the diagnosis of various types of diseases. Forms of data persistence that are currently used in the medical field, mostly, rely on the relational paradigm, which generally support information systems and knowledge that are in hospitals and medical clinics. In this sense, this thesis proposes a new storage model for systems -based medical images. This model was designed from a hierarchical paradigm, following the standard for internationally recognized medical images (DICOM), which also represents the data in a more natural, simplifies the process of search and retrieval. At the end of experiments and after the stages of analysis of the results, the proposed model has shown a better performance when compared to the current model, using relational databases

Availability in the Sprite Distributed File System

In the Sprite environment, tolerating faults means recovering from them quickly. Our position is that performance and availability are the desired features of the typical locally-distributed office/engineering environment, and that very fast server recovery is the most cost-effective way of providing such availability. Mechanisms used for reliability can be inappropriate in systems with the primary goal of performance, and some availability-oriented methods using replicated hardware or processes cost too much for these systems. In contrast, availability via fast recovery need not slow down a system, and our experience in Sprite shows that in some cases the same techniques that provide high performance also provide fast recovery. In our first attempt to reduce file server recovery times to less than 90 seconds, we take advantage of the distributed state already present in our file system, and a high-performance log-structured file system currently under implementation. As a long-term go..

Availability in the Sprite Distributed File System

_ (California Univ.} 5 p N J