75,597 research outputs found
Self-repairing Homomorphic Codes for Distributed Storage Systems
Erasure codes provide a storage efficient alternative to replication based
redundancy in (networked) storage systems. They however entail high
communication overhead for maintenance, when some of the encoded fragments are
lost and need to be replenished. Such overheads arise from the fundamental need
to recreate (or keep separately) first a copy of the whole object before any
individual encoded fragment can be generated and replenished. There has been
recently intense interest to explore alternatives, most prominent ones being
regenerating codes (RGC) and hierarchical codes (HC). We propose as an
alternative a new family of codes to improve the maintenance process, which we
call self-repairing codes (SRC), with the following salient features: (a)
encoded fragments can be repaired directly from other subsets of encoded
fragments without having to reconstruct first the original data, ensuring that
(b) a fragment is repaired from a fixed number of encoded fragments, the number
depending only on how many encoded blocks are missing and independent of which
specific blocks are missing. These properties allow for not only low
communication overhead to recreate a missing fragment, but also independent
reconstruction of different missing fragments in parallel, possibly in
different parts of the network. We analyze the static resilience of SRCs with
respect to traditional erasure codes, and observe that SRCs incur marginally
larger storage overhead in order to achieve the aforementioned properties. The
salient SRC properties naturally translate to low communication overheads for
reconstruction of lost fragments, and allow reconstruction with lower latency
by facilitating repairs in parallel. These desirable properties make
self-repairing codes a good and practical candidate for networked distributed
storage systems
Fine Grained Component Engineering of Adaptive Overlays: Experiences and Perspectives
Recent years have seen significant research being carried out into peer-to-peer (P2P) systems. This work has focused on the styles and applications of P2P computing, from grid computation to content distribution; however, little investigation has been performed into how these systems are built. Component based engineering is an approach that has seen successful deployment in the field of middleware development; functionality is encapsulated in âbuilding blocksâ that can be dynamically plugged together to form complete systems. This allows efficient, flexible and adaptable systems to be built with lower overhead and development complexity. This paper presents an investigation into the potential of using component based engineering in the design and construction of peer-to-peer overlays. It is highlighted that the quality of these properties is dictated by the component architecture used to implement the system. Three reusable decomposition architectures are designed and evaluated using Chord and Pastry case studies. These demonstrate that significant improvements can be made over traditional design approaches resulting in much more reusable, (re)configurable and extensible systems
On Constructing Persistent Identifiers with Persistent Resolution Targets
Persistent Identifiers (PID) are the foundation referencing digital assets in
scientific publications, books, and digital repositories. In its realization,
PIDs contain metadata and resolving targets in form of URLs that point to data
sets located on the network. In contrast to PIDs, the target URLs are typically
changing over time; thus, PIDs need continuous maintenance -- an effort that is
increasing tremendously with the advancement of e-Science and the advent of the
Internet-of-Things (IoT). Nowadays, billions of sensors and data sets are
subject of PID assignment. This paper presents a new approach of embedding
location independent targets into PIDs that allows the creation of
maintenance-free PIDs using content-centric network technology and overlay
networks. For proving the validity of the presented approach, the Handle PID
System is used in conjunction with Magnet Link access information encoding,
state-of-the-art decentralized data distribution with BitTorrent, and Named
Data Networking (NDN) as location-independent data access technology for
networks. Contrasting existing approaches, no green-field implementation of PID
or major modifications of the Handle System is required to enable
location-independent data dissemination with maintenance-free PIDs.Comment: Published IEEE paper of the FedCSIS 2016 (SoFAST-WS'16) conference,
11.-14. September 2016, Gdansk, Poland. Also available online:
http://ieeexplore.ieee.org/document/7733372
A Pragmatic Approach to DHT Adoption
Despite the peer-to-peer community's obvious wish to have its systems adopted, specific mechanisms to facilitate incremental adoption have not yet received the same level of attention as the many other practical concerns associated with these systems. This paper argues that ease of adoption should be elevated to a first-class concern and accordingly presents HOLD, a front-end to existing DHTs that is optimized for incremental adoption. Specifically, HOLD is backwards-compatible: it leverages DNS to provide a key-based routing service to existing Internet hosts without requiring them to install any software. This paper also presents applications that could benefit from HOLD as well as the trade-offs that accompany HOLD. Early implementation experience suggests that HOLD is practical
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A review of miniaturised Non-Destructive Testing technologies for in-situ inspections
Non-destructive testing (NDT) techniques have become attractive trends of product manufacturing, installation and post-maintenance in the aerospace, automotive and manufacturing industry, because of its benefits such as cost saving, easy to use and high efficiency etc. With the industrial products becoming large-scale, high integration and complication, developing the NDT miniaturisation technique for in-situ inspections is highly demanded and becoming an inevitable trend. However, in-situ inspection using NDT have been limited by a number of factors, such as the heavy weight, large size or complex structure etc. This paper aims to systematically identify and analyse the current state-of-the-art of NDT miniaturisation techniques in research and innovation, and discuss the challenge and prospect of miniaturisation of the commonly used NDT techniques
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