@article {43, title = {Evaluating A File Fragmentation System For Multi-provider Cloud Storage}, journal = {SCALABLE COMPUTING. PRACTICE AND EXPERIENCE}, volume = {14}, year = {2013}, pages = {265{\textendash}277}, abstract = {

Currently, storage services represent a new way to do business in Cloud computing. This new trend is proved by the number of Cloud storage providers that are appearing on the market. In this work, we present an innovative approach useful for using different Cloud storage providers in a transparent way, avoiding both data lock-in and possible data privacy violation that can be caused by providers themselves. More specifically, we propose an approach enabling Cloud customers to rely on many Cloud storage providers. Differently from other solutions, with our approach only the customers have the full control of their data, and in addition, if a provider suddenly disappears and/or it is not available anymore, the customers will be able to continue accessing their data, reconstructing them from data fragments replicated in other Cloud storage providers. The paper shows how such an approach works. In particular, experiments, besides proving the goodness of our approach, also provide several guidelines regarding how to properly configure software systems in order to meet the customer{\textquoteright}s requirements (in terms of both QoS and costs).

}, keywords = {Big Data, cloud computing, Confidentiality., Reliability, Storage}, doi = {10.12694/scpe.v14i4.932}, url = {http://www.scpe.org/index.php/scpe/article/view/932/0}, author = {Massimo Villari and Antonio Celesti and Maria Fazio and Antonio Puliafito} } @article {Bruneo2012521, title = {Evaluating wireless sensor node longevity through Markovian techniques}, journal = {Computer Networks - Elsevier }, volume = {56}, number = {2}, year = {2012}, note = {cited By 13}, pages = {521-532}, abstract = {

Wireless sensor networks are constituted of a large number of tiny sensor nodes randomly distributed over a geographical region. In order to reduce power consumption, nodes undergo active-sleep periods that, on the other hand, limit their ability to send/receive data. The aim of this paper is to analyze the longevity of a battery-powered sensor node. A battery discharge model able to capture both linear and non linear discharge processes is presented. Then, two different models are proposed to investigate the longevity, in terms of reliability, of sensor nodes with active-sleep cycles. The first model, well known in the literature, is based on the Markov reward theory and on the evaluation of the accumulated reward distribution. The second model, based on continuous phase type distributions and Kronecker algebra, represents the main contribution of the present work, since it allows to relax some assumptions of the Markov reward model, thus increasing its applicability to more concrete use cases. In the final part of the paper, the results obtained by applying the two techniques to a case study are compared in order to validate and highlight the benefits of our approach and demonstrate the utility of the proposed model in a quite complex and real scenario. {\textcopyright} 2011 Published by Elsevier B.V.

}, keywords = {Algebra, Battery discharge, Continuous phase, Discharge process, Electric network synthesis, Energy utilization, Kronecker algebra, Markov reward, Markov reward model, Markov reward models, Markovian, Randomly distributed, Reliability, Reliability theory, Sensor nodes, Sensors, Wireless sensor node}, issn = {13891286}, doi = {10.1016/j.comnet.2011.10.003}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84856063119\&partnerID=40\&md5=ecbae538bceec8598d787ee3b936a8e1}, author = {Dario Bruneo and Salvatore Distefano and Francesco Longo and Antonio Puliafito and Marco Scarpa} } @proceedings {Bruneo20128, title = {Software rejuvenation in the cloud}, journal = {Proceedings of the 5th International Conference on Simulation Tools and Techniques (SIMUTools)}, year = {2012}, note = {cited By 0; Conference of 5th International Conference on Simulation Tools and Techniques, SIMUTools 2012 ; Conference Date: 19 March 2012 Through 23 March 2012; Conference Code:110134}, pages = {8-16}, publisher = {ICST}, address = {Desenzano del Garda, Italy, 19-23 March 2012}, abstract = {

In this paper, we investigate how software rejuvenation can be used in a Cloud environment to increase the availability of a virtualized system composed of a single virtual machine monitor (VMM) on top of which a certain number of virtual machines (VMs) can be instantiated. We start from the assumption that the aging of a VMM increases with the number of VMs it is managing, thus characterizing the problem in terms of dynamic reliability. Therefore, by identifying the age of the VMM with its reliability and based on the conservation of reliability principle, we characterize the time to failure of the VMM through continuous phase type distributions. The system availability is thus modeled by an expanded continuous time Markov chain expressed in terms of Kronecker algebra in order to face the state space explosion and to keep memory of the age reached by the VMM in case the number of the hosted VMs change. Time-based rejuvenation is taken into consideration and the optimal timer is evaluated in order to maximize the VMM availability. Copyright {\textcopyright} 2012 ICST.

}, keywords = {Availability, cloud computing, Continuous phase type distributions, Continuous time Markov chain, Continuous time systems, Endocrinology, Java programming language, Markov processes, phase type distributions, Rejuvenation, Reliability, Reliability principles, Software rejuvenation, Virtual machine monitors, Virtual reality, Virtualized environment}, isbn = {9781450315104}, doi = {10.4108/icst.simutools.2012.247772}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84922767370\&partnerID=40\&md5=a03b06eec703c94d55c0f4875f181902}, author = {Dario Bruneo and Francesco Longo and Antonio Puliafito and Marco Scarpa and Salvatore Distefano} }