Distributed database

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The atomic commit problem lies at the heart of distributed database systems. The problem consists for a set of processes (database nodes) to agree on whether to commit or abort a transaction (agreement property). The commit decision can only be taken if all processes are initially willing to commit the transaction, and this decision must be taken if all processes are willing to commit and there is no failure (validity property). An atomic commit protocol is said to be non-blocking if every correct process (

Given a replicated database, a divergent design tunes the indexes in each replica differently in order to specialize it for a specific subset of the workload. Empirical studies have shown that this specialization brings significant performance gains compared to the common practice of having the same indexes in all replicas. However, reaping the benefits of divergent designs requires the development of new tuning tools for database administrators, and the existing tools unfortunately suffer from severe short

Given a replicated database, a divergent design tunes the indexes in each replica differently in order to specialize it for a specific subset of the workload. This specialization brings significant performance gains compared to the common practice of having the same indexes in all replicas, but requires the development of new tuning tools for database administrators. In this paper we introduce RITA (Replication-aware Index Tuning Advisor), a novel divergent-tuning advisor that offers several essential featu

With technological advances, the sources of available information have become more and more diverse. Recently, a new source of information has gained growing importance: sensor data. Sensors are devices sensing their environment in various ways and reporti ...

In modern distributed systems, failures are the norm rather than the exception. In many cases, these failures are not benign. Settings such as the Internet might incur malicious (also called Byzantine or arbitrary) behavior and asynchrony. As a result, and ...

The need for high availability and performance in data management systems has been fueling a long running interest in database replication from both academia and industry. However, academic groups often attack replication problems in isolation, overlooking the need for completeness in their solutions, while commercial teams take a holistic approach that often misses opportunities for fundamental innovation. This has created over time a gap between academic research and industrial practice. This paper aims t

The paper presents a primary-backup protocol to manage replicated in-memory database systems (IMDBs). The protocol exploits two features of IMDBs: coarse-grain concurrency control and deferred disk writes. Primary crashes are quickly detected by backups and a new primary is elected whenever the current one is suspected to have failed. False failure suspicions are tolerated and never lead to incorrect behavior. The protocol uses a consensus-like algorithm tailor-made for our replication environment. Under no

Generalized snapshot isolation extends snapshot isolation as used in Oracle and other databases in a manner suitable for replicated databases. While (conventional) snapshot isolation requires that transactions observe the latest'' snapshot of the database, generalized snapshot isolation allows the use of older'' snapshots, facilitating a replicated implementation. We show that many of the desirable properties of snapshot isolation remain. In particular, under certain assumptions on the transaction workl

This paper presents two main contributions: semi-passive replication and Lazy Consensus. The former is a replication technique with parsimonious processing. It is based on the latter; a variant of Consensus allowing the lazy evaluation of proposed values. Semi-passive replication is a replication technique with parsimonious processing. This means that, in the normal case, each request is processed by only one single process. The most significant aspect of semi-passive replication is that it requires a weake

Group communication provides primitives that ensure reliable and ordered delivery of messages to a group of destinations. It is an important building block for replicated fault-tolerant applications such as replicated databases. In the past, most group communication systems have been monolithic. Recent group communication systems have been built around components, allowing for more flexibility. In this paper, we propose a novel approach to the composition of group communication protocols. In this approach,

Database replication protocols have historically been built on top of distributed database systems, and have consequently been designed and implemented using distributed transactional mechanisms, such as atomic commitment. We present the Database State Machine approach, a new way to deal with database replication in a cluster of servers. This approach relies on a powerful atomic broadcast primitive to propagate transactions between database servers, and alleviates the need for atomic commitment. Transaction

Nowadays, networked computers are present in most aspects of everyday life. Moreover, essential parts of society come to depend on distributed systems formed of networked computers, thus making such systems secure and fault tolerant is a top priority. If the particular fault tolerance requirement is high availability, replication of components is a natural choice. Replication is a difficult problem as the state of the replicas must be kept consistent even if some replicas fail, and because in distributed sy

Databases are an important part of today's IT infrastructure: both companies and state institutions rely on database systems to store most of their important data. As we are more and more dependent on database systems, securing this key facility is now a priority. Because of this, research on fault-tolerant database systems is of increasing importance. One way to ensure the fault-tolerance of a system is by replicating it. Replication is a natural way to deal with failures: if one copy is not available, we

This paper addresses the problem of atomic multicasting messages in asynchronous distributed systems. Firstly, we give a characterization of the notion of "genuine atomic multicast''. This characterization leads to a better understanding of the difference between atomic multicast and atomic broadcast, and to make a clear distinction between genuine atomic multicast algorithms and non-genuine atomic multicast algorithms. Secondly, we consider a system with at least two processes among which one can crash, an

Atomic broadcast primitives are often proposed as a mechanism to allow fault-tolerant cooperation between sites in a distributed system. Unfortunately, the delay incurred before a message can be delivered makes it difficult to implement high performance, scalable applications on top of atomic broadcast primitives. Recently, a new approach has been proposed for atomic broadcast which, based on optimistic assumptions about the communication system, reduces the average delay for message delivery to the applica

Since June 1998, EPFL's Visible Human Slice Server (http://visiblehuman.epfl.ch) allows to extract arbitrarily oriented and positioned slices. More than 300,000 slices are extracted each year. In order to give a 3D view of anatomic structures, a new service has been added for extracting slice animations along a user-defined trajectory. This service is useful both for research and teaching purposes (http://visiblehuman.epfl.ch/animation/). Extracting slices of animations at any desired position and orientati

This paper presents x-ability (Exactly-once-ability): a correctness criteria for replicated services. X-ability provides the illusion that the actions executed by a replicated service are executed exactly-once, even if these actions have been actually executed several times and by various replicas. A client can treat a x-able replicated service as if it was not replicated, even if this service executes actions that are non-deterministic and have side-effects on the environment, e.g., invoke other services.

Data replication is an increasingly important topic as databases are more and more deployed over clusters of workstations. One of the challenges in database replication is to introduce replication without severely affecting performance. Because of this difficulty, current database products use lazy replication, which is very efficient but can compromise consistency. As an alternative, eager replication guarantees consistency but most existing protocols have a prohibitive cost. In order to clarify the curren

Distributed database

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How Fast can a Distributed Transaction Commit?

RITA: An index-Tuning advisor for replicated databases

RITA: An Index-Tuning Advisor for Replicated Databases

A Publish/Subscribe Approach to Processing Continuous Queries over Sensor Streams

Abstractions for asynchronous distributed computing with malicious players

Middleware-based Database Replication: The Gaps between Theory and Practice

A Primary-Backup Protocol for In-Memory Database Replication

A Primary-Backup Protocol for In-Memory Database Replication

Generalized Snapshot Isolation and a Prefix-Consistent Implementation

Semi-passive replication and Lazy Consensus

Towards Flexible Finite-State Machine Based Protocol Composition

The Database State Machine Approach

Evaluating the performance of distributed agreement algorithms : tools, methodology and case studies

Group communications and database replication : techniques, issues and performance

Genuine atomic multicast in asynchronous distributed systems

Using Optimistic Atomic Broadcast in Transaction Processing Systems

The visible human slice sequence animation web server

X-ability: A Theory of Replication

Database Replication Techniques: a three parameter classification