Commit Protocols for a Distributed Transactional Memory
ABSTRACT Concurrency control in distributed and parallel applications has been studied for many years but is still an ongoing research topic. Transactional memory addresses this challenge for multicore processors by proposing to execute critical sections as restartable transactions combined with optimistic synchronization. Thus the programmer has not to reason about complex lock management and deadlocks. We believe that some of these ideas are also useful for distributed systems. Therefore, we are developing the Object Sharing Service (OSS) providing transparent data sharing for clusters and grids. OSS supports different consistency models for replica management within one application. In this paper we present the design and implementation of different transaction commit protocols for supporting transactional consistency. The main challenge of the resulting distributed transactional memory (DTM) is how to mask network latency allowing to commit transactions fast. Experiments with synthetic micro benchmarks and a Map Reduce application on the Grid'5000 platform show that a DTM is efficiently providing strong consistency for shared data.
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ABSTRACT: The latest advances in 1550-nm high-speed short-cavity vertical-cavity surface-emitting lasers (VCSELs) are presented. The electrical, optical, and thermal design of these devices is discussed with respect to their high-speed modulation behavior. The implemented design improvements allow high output powers for ambient temperatures up to 90°C, high differential quantum efficiencies up to 40%, temperature-stable single-mode emission, low thermal resistances down to 1.6 K/mW, small-signal modulation bandwidths in excess of 17 GHz, and error-free data transmission at room temperature at data rates of 35 Gb/s in back-to-back configuration and up to 25 Gb/s over 4.2 km of single-mode fiber.IEEE Journal of Selected Topics in Quantum Electronics 11/2011; 17(5-17):1158 - 1166. DOI:10.1109/JSTQE.2011.2109700 · 3.47 Impact Factor
Conference Paper: Smart Replication for In-memory Computations[Show abstract] [Hide abstract]
ABSTRACT: Cloud computing enables diverse new application areas for distributed computing. Many upcoming cloud applications do not fit to simple programming models such as "embarrassing parallelism" but have complex data dependencies and require atomic operations spanning multiple objects. Some large-scale storage systems already implement atomic multiobject operations, but they do not address the complementary problem of efficiently propagating replica updates. In this paper, we present the design and implementation of a smart replication protocol in the ECRAM in-memory storage, which supports atomic multi-object operations. The performance analysis shows that the adaptive mechanism requires much less bandwidth, less memory, and results in improved application performance and responsiveness.Parallel and Distributed Systems (ICPADS), 2012 IEEE 18th International Conference on; 01/2012