1,720,963 research outputs found
Elastic provisioning of virtual Hadoop clusters in OpenStack-based Clouds
No full textMapReduce programming model and its implementations, such as the widely diffused Apache Hadoop framework, are spreading more and more due to their inherent capacity of enabling scalable processing of large-scale datasets. The advent of Cloud has further boosted this trend through the provisioning of virtual Hadoop clusters, easily configurable and accessible according to the Platform as a Service (PaaS) model, deployed over existing Cloud Infrastructure as a Service (IaaS) platforms. However, the coexistence of multiple virtual Hadoop clusters competing for the same shared physical resources requires new management solutions able to dynamically reconfigure and rebalance the placement of Hadoop service components over the virtualized IaaS platform. This paper proposes ESAMAR (Elastic Sahara MApReduce), a novel support based on a cross-layer PaaS-IaaS management approach to transparently grant elasticity and efficiency at the Hadoop PaaS level. ESAMAR monitors the performance of Hadoop clusters at both IaaS and physical layers and exploits load balancing techniques, with full awareness of virtual Hadoop clusters and resources at PaaS/IaaS levels. We deeply assessed our framework in a realistic scenario based on the open source OpenStack; collected results demonstrate the effectiveness and the suitability of our management techniques that contribute to reduce Hadoop job completion time, even under challenging heavy-loaded Cloud system conditions
Virtual network function embedding in real cloud environments
Full text linkFuture network architectures will be completely reshaped by the emerging Network Function Virtualization (NFV) paradigm, and telco operators will likely deploy flexible infrastructures based on the cloud, offering programmable connectivity services and computing/storage facilities in the form of Virtual Data Centers (VDCs). This paper introduces and discusses some challenging technical issues associated with this promising approach, with a special focus on the exploitation of industry-relevant cloud platforms, such as OpenStack, and on network-aware optimal placement problem of entire VDCs, taking into account multiple virtual (Virtual Machines – VMs, virtual networks, ...) and physical (host capacities, network topology and capacity, ...) resources and constraints. The proposed placement, computed for real production OpenStack deployments, not only satisfies the predicted communication for all VDCs deployed atop the same physical data center, but also accounts for the (real) computing overhead due to intense communication load of VMs co-located on the same physical host, such as in the case of Virtual Network Functions (VNF) embedding, typically neglected by similar existing works
Cloud PaaS brokering in action: The Cloud4SOA management infrastructure
No full textIn the last few years, we witnessed a growing interest in interoperability and portability topics within the Cloud Computing area. In fact, most heterogeneous PaaS solutions have been developed with no standard APIs, and with different models and levels of service; in this scenario, vendor lock-in becomes an issue. Cloud4SOA project aims to design and develop a Reference Architecture that could solve interoperability and portability problems within the Cloud domain. This paper describes our work on Cloud4SOA Semantic and SOA layer presenting a common knowledge base framework and a standardized set of harmonized APIs to overcome diversities among PaaS solution and report interesting experimental results collected for two real-world PaaS deployments
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Quality audit and resource brokering for network functions virtualization (NFV) orchestration in hybrid clouds
No full textTechnical and economic opportunities of cloud computing become the focus for Internet applications and at the same time also for telco support infrastructures and network services. In fact, many telco providers are consolidating their service infrastructures towards converged and all-IP next generation networks providing typical telco services within LTE (and soon 5G) and also fixed network environments, e.g., often still adopting IP Multimedia Subsystem (IMS) architecture solutions. This telco service infrastructure evolution requires a significant upfront investment in the necessary hardware and software, thereby slowing down the adoption process significantly more than any other Internet application. Cloud computing applied to telco infrastructures can allow pay-per-use business models and significantly lower investment risks by providing telco infrastructure functionality as Virtual Network Functions (VNFs) on top of a Network Functions Virtualization (NFV) platform. For this purpose we propose a quality audit and resource brokering framework that is fully NFV-compliant. Its current and reported implementation specifically targets IMS services because of the still relevant role played by IMS in converged provisioning and the wide availability of IMS deployment testbeds to validate the proposal. In particular, the proposed solution can monitor the quality offered by VNFs and scale in/out depending on dynamic requirements; it is fully based on industrial standards and open-source reference implementations, thus enabling rapid adoption in real industrial environments
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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