The Experts below are selected from a list of 11358 Experts worldwide ranked by ideXlab platform
Bettina Kemme - One of the best experts on this subject based on the ideXlab platform.
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Database Replication
2010Co-Authors: Bettina Kemme, Ricardo Jimnez Peris, Marta Patio-martnezAbstract:Database Replication is widely used for fault-tolerance, scalability and performance. The failure of one Database replica does not stop the system from working as available replicas can take over the tasks of the failed replica. Scalability can be achieved by distributing the load across all replicas, and adding new replicas should the load increase. Finally, Database Replication can provide fast local access, even if clients are geographically distributed clients, if data copies are located close to clients. Despite its advantages, Replication is not a straightforward technique to apply, and there are many hurdles to overcome. At the forefront is replica control: assuring that data copies remain consistent when updates occur. There exist many alternatives in regard to where updates can occur and when changes are propagated to data copies, how changes are applied, where the Replication tool is located, etc. A particular challenge is to combine replica control with transaction management as it requires several operations to be treated as a single logical unit, and it provides atomicity, consistency, isolation and durability across the replicated system. The book provides a categorization of replica control mechanisms, presents several replica and concurrency control mechanisms in detail, and discusses many of the issues that arise when such solutions need to be implemented within or on top of relational Database systems. Table of Contents: Overview / 1-Copy-Equivalence and Consistency / Basic Protocols / Replication Architecture / The Scalability of Replication / Eager Replication and 1-Copy-Serializability / 1-Copy-Snapshot Isolation / Lazy Replication / Self-Configuration and Elasticity / Other Aspects of Replication
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Database Replication: a tale of research across communities
2010Co-Authors: Bettina Kemme, Gustavo AlonsoAbstract:Replication is a key mechanism to achieve scalability and fault-tolerance in Databases. Its importance has recently been further increased because of the role it plays in achieving elasticity at the Database layer. In Database Replication, the biggest challenge lies in the trade-off between performance and consistency. A decade ago, performance could only be achieved through lazy Replication at the expense of transactional guarantees. The strong consistency of eager approaches came with a high cost in terms of reduced performance and limited scalability. Postgres-R combined results from distributed systems and Databases to develop a Replication solution that provided both scalability and strong consistency. The use of group communication primitives with strong ordering and delivery guarantees together with optimized transaction handling (tailored locking, transferring logs instead of re-executing updates, keeping the message overhead per transaction constant) were a drastic departure from the state-of-the-art at the time. Ten years later, these techniques are widely used in a variety of contexts but particularly in cloud computing scenarios. In this paper we review the original motivation for Postgres-R and discuss how the ideas behind the design have evolved over the years.
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Replication - Database Replication: a tutorial
Lecture Notes in Computer Science, 2010Co-Authors: Bettina Kemme, Marta Patiño-martínez, Ricardo Jiménez-peris, Gustavo AlonsoAbstract:This chapter provides an in-depth introduction to Database Replication, in particular how transactions are executed in a replicated environment. We describe a suite of Replication protocols and illustrate the design alternatives using a two-step approach. We first categorize Replication protocols by only two parameters and present a simple example protocol for each of the resulting categories. Further parameters are then introduced, and we illustrate them by the given Replication protocols and some variants.
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boosting Database Replication scalability through partial Replication and 1 copy snapshot isolation
Pacific Rim International Symposium on Dependable Computing, 2007Co-Authors: Damian Serrano, Marta Patinomartinez, Ricardo Jimenezperis, Bettina KemmeAbstract:Databases have become a crucial component in modern information systems. At the same time, they have become the main bottleneck in most systems. Database Replication protocols have been proposed to solve the scalability problem by scaling out in a cluster of sites. Current techniques have attained some degree of scalability, however there are two main limitations to existing approaches. Firstly, most solutions adopt a full Replication model where all sites store a full copy of the Database. The coordination overhead imposed by keeping all replicas consistent allows such approaches to achieve only medium scalability. Secondly, most Replication protocols rely on the traditional consistency criterion, 1-copy-serializability, which limits concurrency, and thus scalability of the system. In this paper, we first analyze analytically the performance gains that can be achieved by various partial Replication configurations, i.e., configurations where not all sites store all data. From there, we derive a partial Replication protocol that provides 1-copy-snapshot isolation as correctness criterion. We have evaluated the protocol with TPC-W and the results show better scalability than full Replication.
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PRDC - Boosting Database Replication Scalability through Partial Replication and 1-Copy-Snapshot-Isolation
13th Pacific Rim International Symposium on Dependable Computing (PRDC 2007), 2007Co-Authors: Damian Serrano, Ricardo Jiménez-peris, Marta Patiño-martínez, Bettina KemmeAbstract:Databases have become a crucial component in modern information systems. At the same time, they have become the main bottleneck in most systems. Database Replication protocols have been proposed to solve the scalability problem by scaling out in a cluster of sites. Current techniques have attained some degree of scalability, however there are two main limitations to existing approaches. Firstly, most solutions adopt a full Replication model where all sites store a full copy of the Database. The coordination overhead imposed by keeping all replicas consistent allows such approaches to achieve only medium scalability. Secondly, most Replication protocols rely on the traditional consistency criterion, 1-copy-serializability, which limits concurrency, and thus scalability of the system. In this paper, we first analyze analytically the performance gains that can be achieved by various partial Replication configurations, i.e., configurations where not all sites store all data. From there, we derive a partial Replication protocol that provides 1-copy-snapshot isolation as correctness criterion. We have evaluated the protocol with TPC-W and the results show better scalability than full Replication.
Cipria Tutu - One of the best experts on this subject based on the ideXlab platform.
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On the Path from Total Order to Database Replication
2004Co-Authors: Yair Amir, Cipria TutuAbstract:We introduce ZBCast, a primitive that provides Persistent Global Total Order for messages delivered to a group of participants that can crash and subsequently recover and that can become temporarily partitioned and then remerge due to network conditions. The paper presents in detail and proves the correctness of an efficient algorithm that implements ZBCast on top of existing group communication infrastructure. The algorithm minimizes the amount of required forced disk writes and avoids the need for application level (end-to-end) acknowledgments per message. We also present an extension of the algorithm that allows dynamic addition or removal of participants. We indicate how ZBCast can be employed to build a generic data Replication engine that can be used to provide consistent synchronous Database Replication. We provide experimental results that indicate the efficiency of the approach.
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on the performance of consistent wide area Database Replication
2003Co-Authors: Yair Amirclaudiu Danilovmichal Miskinamir, Jonathan Stanton, Cipria TutuAbstract:In this paper we design a generic, consistent Replication architecture that enables transparent Database Replication and we present the optimizations and tradeoffs of the chosen design. We demonstrate the practicality of our approach by building a prototype that replicates a PostgreSQL Database system. We provide experimental results for consistent wide-area Database Replication. We claim that the use of an optimized synchronization engine is the key to building a practical synchronous Replication system for wide-area network settings.
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from total order to Database Replication
International Conference on Distributed Computing Systems, 2002Co-Authors: Yair Amir, Cipria TutuAbstract:This paper presents in detail an efficient and provably correct algorithm for Database Replication over partitionable networks. Our algorithm avoids the need for end-to-end acknowledgments for each action while supporting network partitions and merges and allowing dynamic instantiation of new replicas. One round of end-to-end acknowledgments is required only upon a membership change event such as a network partition. New actions may be introduced to the system at any point, not only while in a primary component. We show how performance can be further improved for applications that allow relaxation of consistency requirements. We provide experimental results that demonstrate the efficiency of our approach.
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on the performance of wide area synchronous Database Replication
2002Co-Authors: Yai Ami, Claudiu Danilov, Michal Miskinami, Jonatha Stanto, Cipria TutuAbstract:A fundamental challenge in Database Replication is to maintain a low cost of updates while assuring global system consistency. The dicult y of the problem is magnied for wide-area network settings due to the high latency and the increased likelihood of network partitions. As a consequence, most of the research in the area has focused either on improving the performance of local transaction execution or on Replication models with weaker semantics, which rely on application knowledge to resolve potential conicts. In this work we identify the performance bottleneck of the existing synchronous Replication schemes as residing in the update synchronization algorithm. We compare the performance of several such synchronization algorithms and highlight the large performance gap between various methods. We design a generic, synchronous Replication scheme that uses an enhanced synchronization algorithm and demonstrate its practicality by building a prototype that replicates a PostgreSQL Database system. We claim that the use of an optimized synchronization engine is the key to building a practical synhronous Replication system for wide-area network settings.
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Practical Wide-Area Database Replication 1
2002Co-Authors: Yair Amir, Claudiu Danilov, Cipria Tutu, Jonathan Stanton, Michal Miskin-amir, Spread Concepts Llc, Acacia AveAbstract:This paper explores the architecture, implementation and performance of a wide and local area Database Replication system. The architecture provides peer Replication, supporting diverse application semantics, based on a group communication paradigm. Network partitions and merges, computer crashes and recoveries, and message omissions are all handled. Using a generic Replication engine and the Spread group communication toolkit, we provide Replication services for the PostgreSQL Database system. We define three different environments to be used as test-beds: a local area cluster, a wide area network that spans the U.S.A, and an emulated wide area test bed. We conduct an extensive set of experiments on these environments, varying the number of replicas and clients, the mix of updates and queries, and the network latency. Our results show that sophisticated algorithms and careful distributed systems design can make symmetric, synchronous, peer Database Replication a reality for both local and wide area networks.
Francesc D. Muñoz-escoí - One of the best experts on this subject based on the ideXlab platform.
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ICSOFT (Selected Papers) - A Hybrid Approach for Database Replication: Finding the Optimal Configuration between Update Everywhere and Primary Copy Paradigms
Communications in Computer and Information Science, 2011Co-Authors: M. Liroz-gistau, José Enrique Armendáriz-iñigo, J. R. González De Mendívil, J. R. Juárez-rodríguez, Francesc D. Muñoz-escoíAbstract:Database Replication has been subject of two different approaches, namely primary copy and update everywhere protocols. The former only allows performing update transactions in the primary replica, while the rest are only used to execute read-only transactions. Update everywhere protocols, on the other hand, allow the system to schedule update transactions in any replica, thus increasing its capacity to deal with update intensive workloads and overcoming failures. However, synchronization costs augment and its throughput may fall below the ones obtained by primary copy approaches. Under these circumstances, we propose a new Database Replication paradigm, halfway between primary copy and update everywhere approaches, which improve system’s performance by adapting its configuration depending on the workload submitted to the system. The core of this approach is a deterministic Replication protocol which propagate changes so that broadcast transactions are never aborted. We also propose a recovery algorithm to ensure fault tolerance.
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Correctness proof of a Database Replication protocol under the perspective of the I/O automaton model
Acta Informatica, 2009Co-Authors: José Enrique Armendáriz-iñigo, José Ramón González De Mendívil, José Ramón Garitagoitia, Francesc D. Muñoz-escoíAbstract:Correctness of recent Database Replication protocols has been justified in a rather informal way focusing only in safety properties and without using any rigorous formalism. Since a Database Replication protocol must ensure some degree of replica consistency and that transactions follow a given isolation level, previous proofs only focused in these two issues. This paper proposes a formalization using the I/O automaton model, identifying several components in the distributed system that are involved in the Replication support (Replication protocol, group communication system, Database replicas) and specifying clearly their actions in the global replicated system architecture. Then, a general certification-based Replication protocol guaranteeing the snapshot isolation level is proven correct. To this end, different safety and liveness properties are identified, checked and proved. Our work shows that some details of the Replication protocols that were ignored in previous correctness justifications are indeed needed in order to guarantee our proposed correctness criteria.
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SRDS - Performance Evaluation of a Metaprotocol for Database Replication Adaptability
2009 28th IEEE International Symposium on Reliable Distributed Systems, 2009Co-Authors: M. I. Ruiz-fuertes, Francesc D. Muñoz-escoíAbstract:Common solutions to Database Replication use a single Replication protocol. This approach lacks flexibility for changing scenarios or when dealing with heterogeneous client application requirements. Our proposal is a metaprotocol that supports several Replication protocols which may follow different Replication techniques or provide different isolation levels. With our metaprotocol, Replication protocols can either work concurrently with the same data or be sequenced for adapting to dynamic environments. Experimental results demonstrate its low overhead and measure the influence of protocol concurrency on system performance.
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SAC - SIPRe: a partial Database Replication protocol with SI replicas
Proceedings of the 2008 ACM symposium on Applied computing - SAC '08, 2008Co-Authors: José Enrique Armendáriz-iñigo, A. Mauch-goya, J. R. González De Mendívil, Francesc D. Muñoz-escoíAbstract:Database Replication has been researched as a solution to overcome the problems of performance and availability of distributed systems. Full Database Replication, based on group communication systems, is an attempt to enhance performance that works well for a reduced number of sites. If application locality is taken into consideration, partial Replication, i.e. not all sites store the full Database, also enhances scalability. On the other hand, it is needed to keep all copies consistent. If each DBMS provides SI, the execution of transactions has to be coordinated so as to obtain Generalized-SI (GSI). In this paper, a partial Replication protocol providing GSI is introduced that gives a consistent view of the Database, providing an adaptive Replication technique and supporting the failure and recovery of replicas.
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OTM Conferences (1) - Extending Middleware Protocols for Database Replication with Integrity Support
On the Move to Meaningful Internet Systems: OTM 2008, 2008Co-Authors: Francesc D. Muñoz-escoí, José Enrique Armendáriz-iñigo, Hendrik Decker, M. I. Ruiz-fuertes, Jose Ramon Gonzalez De MendivilAbstract:Current middleware Database Replication protocols take care of read-write conflict evaluation. If there are no such conflicts, protocols sanction transactions to commit. Other conflicts may arise due to integrity violation. So, if, in addition to the consistency of transactions and replicas, also the consistency of integrity constraints is to be supported, some more care must be taken. Some classes of Replication protocols are able to seamlessly deal with the integrity support of the underlying DBMS, but others are not. In this paper, we analyze the support for integrity that can be provided in various classes of Replication protocols. Also, we propose extensions for those that cannot directly manage certain kinds of constraints that are usually supported in DBMSs.
Nuno Preguica - One of the best experts on this subject based on the ideXlab platform.
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efficient middleware for byzantine fault tolerant Database Replication
European Conference on Computer Systems, 2011Co-Authors: Rui Garcia, Rodrigo Rodrigues, Nuno PreguicaAbstract:Byzantine fault tolerance (BFT) enhances the reliability and availability of replicated systems subject to software bugs, malicious attacks, or other unexpected events. This paper presents Byzantium, a BFT Database Replication middleware that provides snapshot isolation semantics. It is the first BFT Database system that allows for concurrent transaction execution without relying on a centralized component, which is essential for having both performance and robustness. Byzantium builds on an existing BFT library but extends it with a set of techniques for increasing concurrency in the execution of operations, for optimistically executing operations in a single replica, and for striping and load-balancing read operations across replicas. Experimental results show that our Replication protocols introduce only a modest performance overhead for read-write dominated workloads and perform better than a non-replicated Database system for read-only workloads.
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EuroSys - Efficient middleware for byzantine fault tolerant Database Replication
Proceedings of the sixth conference on Computer systems - EuroSys '11, 2011Co-Authors: Rui Garcia, Rodrigo Rodrigues, Nuno PreguicaAbstract:Byzantine fault tolerance (BFT) enhances the reliability and availability of replicated systems subject to software bugs, malicious attacks, or other unexpected events. This paper presents Byzantium, a BFT Database Replication middleware that provides snapshot isolation semantics. It is the first BFT Database system that allows for concurrent transaction execution without relying on a centralized component, which is essential for having both performance and robustness. Byzantium builds on an existing BFT library but extends it with a set of techniques for increasing concurrency in the execution of operations, for optimistically executing operations in a single replica, and for striping and load-balancing read operations across replicas. Experimental results show that our Replication protocols introduce only a modest performance overhead for read-write dominated workloads and perform better than a non-replicated Database system for read-only workloads.
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byzantium byzantine fault tolerant Database Replication providing snapshot isolation
Hot Topics in System Dependability, 2008Co-Authors: Nuno Preguica, Rodrigo Rodrigues, Cristovao Honorato, Joao LourencoAbstract:Database systems are a key component behind many of today's computer systems. As a consequence, it is crucial that Database systems provide correct and continuous service despite unpredictable circumstances, such as software bugs or attacks. This paper presents the design of Byzantium, a Byzantine fault-tolerant Database Replication middleware that provides snapshot isolation (SI) semantics. SI is very popular because it allows increased concurrency when compared to serializability, while providing similar behavior for typical workloads. Thus, Byzantium improves on existing proposals by allowing increased concurrency and not relying on any centralized component. Our middleware can be used with off-the-shelf Database systems and it is built on top of an existing BFT library.
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HotDep - Byzantium: Byzantine-fault-tolerant Database Replication providing snapshot isolation
2008Co-Authors: Nuno Preguica, Rodrigo Rodrigues, Cristovao Honorato, Joao LourencoAbstract:Database systems are a key component behind many of today's computer systems. As a consequence, it is crucial that Database systems provide correct and continuous service despite unpredictable circumstances, such as software bugs or attacks. This paper presents the design of Byzantium, a Byzantine fault-tolerant Database Replication middleware that provides snapshot isolation (SI) semantics. SI is very popular because it allows increased concurrency when compared to serializability, while providing similar behavior for typical workloads. Thus, Byzantium improves on existing proposals by allowing increased concurrency and not relying on any centralized component. Our middleware can be used with off-the-shelf Database systems and it is built on top of an existing BFT library.
Javam C Machado - One of the best experts on this subject based on the ideXlab platform.
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towards elastic multi tenant Database Replication with quality of service
Utility and Cloud Computing, 2012Co-Authors: Flavio R C Sousa, Javam C MachadoAbstract:Database systems serving cloud platforms must handle a large number of applications or tenants. Multi-tenancy Database has been prevalent for hosting multiple tenants within a single DBMS while enabling effective resource sharing. Providing such performance goals is challenging for providers as they must balance the performance that they can deliver to tenants and the operating costs. In such Database systems, a key functionality for service providers is Database Replication, which is useful for availability, performance, elasticity, and quality of service. This paper presents RepliC, an approach to Database Replication in the cloud with quality of service, elasticity, and support tomulti-tenancy. In order to evaluate RepliC, some experiments that measure the quality of service and elasticity are presented. Our experiment results confirm that RepliC ensures the quality of service with small SLA violations, while using resources efficiently.
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UCC - Towards Elastic Multi-Tenant Database Replication with Quality of Service
2012 IEEE Fifth International Conference on Utility and Cloud Computing, 2012Co-Authors: Flavio R C Sousa, Javam C MachadoAbstract:Database systems serving cloud platforms must handle a large number of applications or tenants. Multi-tenancy Database has been prevalent for hosting multiple tenants within a single DBMS while enabling effective resource sharing. Providing such performance goals is challenging for providers as they must balance the performance that they can deliver to tenants and the operating costs. In such Database systems, a key functionality for service providers is Database Replication, which is useful for availability, performance, elasticity, and quality of service. This paper presents RepliC, an approach to Database Replication in the cloud with quality of service, elasticity, and support tomulti-tenancy. In order to evaluate RepliC, some experiments that measure the quality of service and elasticity are presented. Our experiment results confirm that RepliC ensures the quality of service with small SLA violations, while using resources efficiently.
