Version stamps-decentralized version vectors

Almeida, Paulo Sérgio; Baquero, Carlos; Fonte, Victor

doi:10.1109/icdcs.2002.1022304

Cited by 17 publications

(11 citation statements)

References 14 publications

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“…6.4.1 Version timestamps. Version timestamps (VTs) are a technique used in the Panasync file replicator [Almeida et al 2002;Almeida et al 2000]. They adapt VVs to environments with frequent replica creation and removal.…”

Section: Vector Clocks and Their Variationsmentioning

confidence: 99%

Optimistic replication

2005

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Data replication is a key technology in distributed data sharing systems, enabling higher availability and performance. This paper surveys optimistic replication algorithms that allow replica contents to diverge in the short term, in order to support concurrent work practices and to tolerate failures in low-quality communication links. The importance of such techniques is increasing as collaboration through wide-area and mobile networks becomes popular.Optimistic replication techniques are different from traditional "pessimistic" ones. Instead of synchronous replica coordination, an optimistic algorithm propagates changes in the background, discovers conflicts after they happen and reaches agreement on the final contents incrementally.We explore the solution space for optimistic replication algorithms. This paper identifies key challenges facing optimistic replication systems -ordering operations, detecting and resolving conflicts, propagating changes efficiently, and bounding replica divergence -and provides a comprehensive survey of techniques developed for addressing these challenges.

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Section: Vector Clocks and Their Variationsmentioning

confidence: 99%

Optimistic replication

2005

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“…Almeida, Baquero, and Fonte [3] do not use local agreement events, as we do, but rather represent reconciliation in a manner that is fundamentally quite similar to a version vector approach that would take the pointwise maximum for agreement events. However, in a restriction reminiscent of our reciprocality requirement, they only consider synchronous synchronization (both replicas synchronize at the same time).…”

Section: Related Workmentioning

confidence: 99%

“…Almeida et al [3] address the problem of efficiently representing version vectors when replicas can leave and join the system. Almeida, and Baquero [1] show that version vectors can be represented using only a bounded amount of information per replica, when they are only being used to check dominance or conflict between current versions of data in a distributed system.…”

Section: Related Workmentioning

confidence: 99%

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Agreeing to Agree: Conflict Resolution for Optimistically Replicated Data

Greenwald

Khanna

Kunal

et al. 2006

Lecture Notes in Computer Science

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Current techniques for reconciling disconnected changes to optimistically replicated data often use version vectors or related mechanisms to track causal histories. This allows the system to tell whether the value at one replica dominates another or whether the two replicas are in conflict. However, current algorithms do not provide entirely satisfactory ways of repairing conflicts. The usual approach is to introduce fresh events into the causal history, even in situations where the causally independent values at the two replicas are actually equal. In some scenarios these events may later conflict with each other or with further updates, slowing or even preventing convergence of the whole system.To address this issue, we enrich the set of possible actions at a replica to include a notion of explicit conflict resolution between existing events, where the user at a replica declares that one set of events dominates another, or that a set of events are equivalent. We precisely specify the behavior of this refined replication framework from a user's point of view and show that, if communication is assumed to be "reciprocal" (with pairs of replicas exchanging information about their current states), then this specification can be implemented by an algorithm with the property that the information stored at any replica and the sizes of the messages sent between replicas are bounded by a polynomial function of the number of replicas in the system.

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“…The management of version vectors becomes complicated since entries for newly added sites have to be propagated to other replica sites [2,15,18,16]. This problem is especially pronounced for peer-to-peer sharing of mutable data where it is reasonable to assume a given object has tens of authors and thousands of readers.…”

Section: Introductionmentioning

confidence: 99%