156 research outputs found
CATS: linearizability and partition tolerance in scalable and self-organizing key-value stores
Distributed key-value stores provide scalable, fault-tolerant, and self-organizing
storage services, but fall short of guaranteeing linearizable consistency
in partially synchronous, lossy, partitionable, and dynamic networks, when data
is distributed and replicated automatically by the principle of consistent hashing.
This paper introduces consistent quorums as a solution for achieving atomic
consistency. We present the design and implementation of CATS, a distributed
key-value store which uses consistent quorums to guarantee linearizability and partition tolerance in such adverse and dynamic network conditions. CATS is
scalable, elastic, and self-organizing; key properties for modern cloud storage
middleware. Our system shows that consistency can be achieved with practical
performance and modest throughput overhead (5%) for read-intensive workloads
A termination protocol for simple network partitioning in distributed database systems
Resilient commit protocols for multisite simple network partitioning are studied in this paper. The necessity of termination protocols to make commit protocols resilient in multisite simple network partitioning is presented. A termination protocol that makes the three-phase commit protocol resilient is designed. This protocol is valid even for transient network partitioning. The method can be generalized to design termination protocols for other commit protocols in multisite simple network partitioning.published_or_final_versio
Optimal Termination Protocols for Network Partitioning
We address the problem of maintaining the distributed database consistency in presence of failures while maximizing the database availability. Network partitioning is a failure which partitions the distributed system into a number of parts, no part being able to communicate with any other. Formalizations of various notions in this context are developed and two measures for the performances of protocols in presence of a network partitioning are introduced. A general optimality theory is developed for two classes of protocols - centralized and decentralized. Optimal protocols are produced in all cases.published_or_final_versio
Pretty Private Group Management
Group management is a fundamental building block of today's Internet
applications. Mailing lists, chat systems, collaborative document edition but
also online social networks such as Facebook and Twitter use group management
systems. In many cases, group security is required in the sense that access to
data is restricted to group members only. Some applications also require
privacy by keeping group members anonymous and unlinkable. Group management
systems routinely rely on a central authority that manages and controls the
infrastructure and data of the system. Personal user data related to groups
then becomes de facto accessible to the central authority. In this paper, we
propose a completely distributed approach for group management based on
distributed hash tables. As there is no enrollment to a central authority, the
created groups can be leveraged by various applications. Following this
paradigm we describe a protocol for such a system. We consider security and
privacy issues inherently introduced by removing the central authority and
provide a formal validation of security properties of the system using AVISPA.
We demonstrate the feasibility of this protocol by implementing a prototype
running on top of Vuze's DHT
An Integrated Distributed Storage Design Offering Data Retrievability and Recoverability Using Soft Decision Decoding of Block Codes
Active distributed storages need to assure both consistency and dynamic data support, in addition to availability, confidentiality and resiliency. Further, since storage durability suffers in untrusted and unreliable environments, it becomes crucial to (a) select the most reliable set of servers to assure data retrievability and (b) dynamically identify errant servers and restore the data to ensure data recoverability. We address the issues of concurrency, consistency, dynamic data support, data share repair, and trust management in providing persistent storage and access. The paper focuses primarily on erasure coded distributed storages (storages employing erasure coding for data dispersal). Integration of Quorum based approach using Notification propagation, with a reliability model based on server trust-reputation forms the comprehensive design proposed. Treating servers and their data shares equally at data reconstructions during data retrievals is rather inadequate in untrusted environments. The design provides a suitable platform for use of Soft Decision Decoding to overcome this inadequacy. The design has been validated by the simulation, study, and analysis carried out for Reed Solomon coded storage with varying levels of resiliency and concurrency. The proposed design can be suitably adapted in typical distributed information storages catering to global networked audience in public, untrusted, and unreliable operating environments.</p
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