3,260 research outputs found

    Alpha Entanglement Codes: Practical Erasure Codes to Archive Data in Unreliable Environments

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    Data centres that use consumer-grade disks drives and distributed peer-to-peer systems are unreliable environments to archive data without enough redundancy. Most redundancy schemes are not completely effective for providing high availability, durability and integrity in the long-term. We propose alpha entanglement codes, a mechanism that creates a virtual layer of highly interconnected storage devices to propagate redundant information across a large scale storage system. Our motivation is to design flexible and practical erasure codes with high fault-tolerance to improve data durability and availability even in catastrophic scenarios. By flexible and practical, we mean code settings that can be adapted to future requirements and practical implementations with reasonable trade-offs between security, resource usage and performance. The codes have three parameters. Alpha increases storage overhead linearly but increases the possible paths to recover data exponentially. Two other parameters increase fault-tolerance even further without the need of additional storage. As a result, an entangled storage system can provide high availability, durability and offer additional integrity: it is more difficult to modify data undetectably. We evaluate how several redundancy schemes perform in unreliable environments and show that alpha entanglement codes are flexible and practical codes. Remarkably, they excel at code locality, hence, they reduce repair costs and become less dependent on storage locations with poor availability. Our solution outperforms Reed-Solomon codes in many disaster recovery scenarios.Comment: The publication has 12 pages and 13 figures. This work was partially supported by Swiss National Science Foundation SNSF Doc.Mobility 162014, 2018 48th Annual IEEE/IFIP International Conference on Dependable Systems and Networks (DSN

    Dependability of E-Information Sources

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    Multiresolutional Fault-Tolerant Sensor Integration and Object Recognition in Images.

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    This dissertation applies multiresolution methods to two important problems in signal analysis. The problem of fault-tolerant sensor integration in distributed sensor networks is addressed, and an efficient multiresolutional algorithm for estimating the sensors\u27 effective output is proposed. The problem of object/shape recognition in images is addressed in a multiresolutional setting using pyramidal decomposition of images with respect to an orthonormal wavelet basis. A new approach to efficient template matching to detect objects using computational geometric methods is put forward. An efficient paradigm for object recognition is described

    Durability and Availability of Erasure-Coded Storage Systems with Concurrent Maintenance

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    This initial version of this document was written back in 2014 for the sole purpose of providing fundamentals of reliability theory as well as to identify the theoretical types of machinery for the prediction of durability/availability of erasure-coded storage systems. Since the definition of a "system" is too broad, we specifically focus on warm/cold storage systems where the data is stored in a distributed fashion across different storage units with or without continuous operation. The contents of this document are dedicated to a review of fundamentals, a few major improved stochastic models, and several contributions of my work relevant to the field. One of the contributions of this document is the introduction of the most general form of Markov models for the estimation of mean time to failure. This work was partially later published in IEEE Transactions on Reliability. Very good approximations for the closed-form solutions for this general model are also investigated. Various storage configurations under different policies are compared using such advanced models. Later in a subsequent chapter, we have also considered multi-dimensional Markov models to address detached drive-medium combinations such as those found in optical disk and tape storage systems. It is not hard to anticipate such a system structure would most likely be part of future DNA storage libraries. This work is partially published in Elsevier Reliability and System Safety. Topics that include simulation modelings for more accurate estimations are included towards the end of the document by noting the deficiencies of the simplified canonical as well as more complex Markov models, due mainly to the stationary and static nature of Markovinity. Throughout the document, we shall focus on concurrently maintained systems although the discussions will only slightly change for the systems repaired one device at a time.Comment: 58 pages, 20 figures, 9 tables. arXiv admin note: substantial text overlap with arXiv:1911.0032
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