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- In 2010 International Conference on Distributed Computing Systems , 2010
"... �bstract—In peer-to-peer storage systems, peers replicate each others ’ data in order to increase availability. If the matching is done centrally, the algorithm can optimize data availability in an equitable manner for all participants. However, if matching is decentralized, the peers ’ selfishness ..."
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�bstract—In peer-to-peer storage systems, peers replicate each others ’ data in order to increase availability. If the matching is done centrally, the algorithm can optimize data availability in an equitable manner for all participants. However, if matching is decentralized, the peers ’ selfishness can greatly alter the results, leading to performance inequities that can render the system unreliable and thus ultimately unusable. We analyze the problem using both theoretical approaches �complexity analysis for the centralized system, game theory for the decentralized one) and simulation. We prove that the problem of optimizing availability in a centralized system is NP-hard. In decentralized settings, we show that the rational behavior of selfish peers will be to replicate only with similarly-available peers. Compared to the socially-optimal solution, highly available peers have their data availability increased at the expense of decreased data availability for less available peers. The price of anarchy is high: unbounded in one model, and linear with the number of time slots in the second model. We also propose centralized and decentralized heuristics that, according to our experiments, converge fast in the average case. The high price of anarchy means that a completely decentralized system could be too hostile for peers with low availability, who could never achieve satisfying replication parameters. Moreover, we experimentally show that even explicit consideration and exploitation of diurnal patterns of peer availability has a small effect on the data availability—except when the system has truly global scope. Yet a fully centralized system is infeasible, not only because of problems in information gathering, but also the complexity of optimizing availability. The solution to this dilemma is to create system-wide cooperation rules that allow a decentralized algorithm, but also limit the selfishness of the participants. Index Terms—price of anarchy, equitable optimization, distributed storage I.
A Secure Peer-to-Peer Backup Service Keeping Great Autonomy while under the Supervision of a Provider
"... Making backup is so cumbersome and expensive that individuals hardly ever backup their data and companies usually duplicate their data into a secondary server. This paper proposes a novel Peer-to-Peer (P2P) backup system known as the SecureBackup service, which was defined in the DisPairse research ..."
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Making backup is so cumbersome and expensive that individuals hardly ever backup their data and companies usually duplicate their data into a secondary server. This paper proposes a novel Peer-to-Peer (P2P) backup system known as the SecureBackup service, which was defined in the DisPairse research project. It utilizes the unused personal hard disk spaces attached to the Internet to implement a distributed backup service that is reliable, performant, and secure. Additionally to the existing approaches like pStore [Batten et al. 2001], Pastiche [Landon et al. 2002], and PeerStore [Landers et al. 2004], addressing the integrity, confidentiality and availability of data in a P2P backup system, the SecureBackup service implements the access control of the peers to the service, the detection of malicious peers, the evaluation of the reliability level of each peer, the rewarding or charging of the peers for the consumed resources or the resources they made available, and the incentives for peers to actively participate to the service. SecureBackup is mainly characterized by a newly meta-data structure for backup file, and a centralized node, under the control of the service provider, which supervises the Authentication, Authorization and Accounting (AAA) services and the operations of the system. While designing a centralized architecture, we paid attention to preserve the autonomy of the P2P backup service. According to some experiments made on few peer nodes, we are confident that the introduced security mechanisms do not much penalize the performances of the system.
"... c t i v it y e p o r t 2008 Table of contents ..."