6,620 research outputs found
Middleware-based Database Replication: The Gaps between Theory and Practice
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 to characterize the gap along three axes: performance,
availability, and administration. We build on our own experience developing and
deploying replication systems in commercial and academic settings, as well as
on a large body of prior related work. We sift through representative examples
from the last decade of open-source, academic, and commercial database
replication systems and combine this material with case studies from real
systems deployed at Fortune 500 customers. We propose two agendas, one for
academic research and one for industrial R&D, which we believe can bridge the
gap within 5-10 years. This way, we hope to both motivate and help researchers
in making the theory and practice of middleware-based database replication more
relevant to each other.Comment: 14 pages. Appears in Proc. ACM SIGMOD International Conference on
Management of Data, Vancouver, Canada, June 200
A Massively Scalable Architecture For Instant Messaging & Presence
This paper analyzes the scalability of Instant Messaging & Presence (IM&P) architectures. We take a queueing-based modelling and analysis approach to find the bottlenecks of the current IM&P architecture at the Dutch social network Hyves, as well as of alternative architectures. We use the Hierarchical Evaluation Tool (HIT) to create and analyse models analytically. Based on these results, we recommend a new architecture that provides better scalability than the current one. \u
Interest-based RDF Update Propagation
Many LOD datasets, such as DBpedia and LinkedGeoData, are voluminous and
process large amounts of requests from diverse applications. Many data products
and services rely on full or partial local LOD replications to ensure faster
querying and processing. While such replicas enhance the flexibility of
information sharing and integration infrastructures, they also introduce data
duplication with all the associated undesirable consequences. Given the
evolving nature of the original and authoritative datasets, to ensure
consistent and up-to-date replicas frequent replacements are required at a
great cost. In this paper, we introduce an approach for interest-based RDF
update propagation, which propagates only interesting parts of updates from the
source to the target dataset. Effectively, this enables remote applications to
`subscribe' to relevant datasets and consistently reflect the necessary changes
locally without the need to frequently replace the entire dataset (or a
relevant subset). Our approach is based on a formal definition for
graph-pattern-based interest expressions that is used to filter interesting
parts of updates from the source. We implement the approach in the iRap
framework and perform a comprehensive evaluation based on DBpedia Live updates,
to confirm the validity and value of our approach.Comment: 16 pages, Keywords: Change Propagation, Dataset Dynamics, Linked
Data, Replicatio
Eventual Consistency: Origin and Support
Eventual consistency is demanded nowadays in geo-replicated services that need to be highly scalable and available. According to the CAP constraints, when network partitions may arise, a distributed service should choose between being strongly consistent or being highly available. Since scalable services should be available, a relaxed consistency (while the network is partitioned) is the preferred choice. Eventual consistency is not a common data-centric consistency model, but only a state convergence condition to be added to a relaxed consistency model. There are still several aspects of eventual consistency that have not been analysed in depth in previous works: 1. which are the oldest replication proposals providing eventual consistency, 2. which replica consistency models provide the best basis for building eventually consistent services, 3. which mechanisms should be considered for implementing an eventually consistent service, and 4. which are the best combinations of those mechanisms for achieving different concrete goals. This paper provides some notes on these important topics
A formal characterization of SI-based ROWA replication protocols
Snapshot isolation (SI) is commonly used in some commercial DBMSs with a multiversion
concurrency control mechanism since it never blocks read-only transactions. Recent database
replication protocols have been designed using SI replicas where transactions are firstly
executed in a delegate replica and their updates (if any) are propagated to the rest of the
replicas at commit time; i.e. they follow the Read One Write All (ROWA) approach. This paper
provides a formalization that shows the correctness of abstract protocols which cover these
replication proposals. These abstract protocols differ in the properties demanded for achieving
a global SI level and those needed for its generalized SI (GSI) variant ¿ allowing reads from old
snapshots. Additionally, we propose two more relaxed properties that also ensure a global GSI
level. Thus, some applications can further optimize their performance in a replicated system
while obtaining GSI.
© 2010 Elsevier B.V. All rights reserved.The authors wish to thank the reviewers for their valuable comments that helped us to greatly improve the quality and readability of this paper. This work has been supported by the Spanish Government under research grant TIN2009-14460-C03. Besides, the authors wish to thank the reviewers for their valuable comments that helped us to greatly improve the quality and readability of this paper.Armendáriz-Iñigo, J.; Juárez-Rodríguez, J.; González De Mendívil, J.; Garitagoitia, J.; Irún Briz, L.; Muñoz Escoí, FD. (2011). A formal characterization of SI-based ROWA replication protocols. Data and Knowledge Engineering. 70(1):21-34. doi:10.1016/j.datak.2010.07.012S213470
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