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New post-doc

We welcome Dr. Miguel Branco as a new member of DIAS lab.

Posted by Manos Athanassoulis at 16:53
Dr. Kantere moved to Cyprus as a tenure-track lecturer.

Dr. Kantere moved to Cyprus as a tenure-track lecturer.

Posted by Manos Athanassoulis at 16:52
Three new PhD students

We have three new PhD students this semester. Pinar Tozun joined as a second year PhD student, and Danica Porobic and Renata Borovica, joined as first year PhD students.

Posted by Manos Athanassoulis at 16:47
Two papers presented, VLBD 2010

Data-Oriented Transaction Execution and Aether: A scalable approach to logging were presented at VLDB 2010, Singapore.


Data-Oriented Transaction Execution
While hardware technology has  undergone major advancements over the past decade, transaction processing systems have remained largely unchanged. The number of cores on a chip grows exponentially, following Moore's Law, allowing for an everincreasing number of transactions to execute in parallel. As the number of concurrently-executing transactions increases, contended critical sections become scalability burdens. In typical transaction processing systems the centralized lock manager is often the first contended component and scalability bottleneck. In this paper, we identify the conventional thread-totransaction assignment policy as the primary cause of contention. Then, we design DORA, a system that decomposes each transaction to smaller actions and assigns actions to threads based on which data each action is  about to access. DORA’s design allows each thread to mostly access thread-local data structures, minimizing interaction with the contention-prone centralized lock manager. Built on top of a conventional storage engine, DORA maintains all the ACID properties. Evaluation of a prototype implementation of DORA on a multicore system demonstrates that DORA attains up to 4.8x higher throughput than a state-of-the-art storage engine when running a variety of synthetic and real-world OLTP workloads. 
Aether: A scalable approach to logging
The shift to multi-core hardware brings new challenges to database systems, as the software parallelism determines performance. Even though database systems traditionally accommodate simultaneous requests, a multitude of synchronization barriers serialize execution. Write-ahead logging is a fundamental, omnipresent component in ARIES-style concurrency and recovery, and one of the most important yet-to-be addressed potential bottlenecks, especially in OLTP workloads making frequent small changes to data. In this paper, we identify four logging-related impediments to database system scalability. Each issue challenges different level in the software architecture: (a) the high volume of small-sized I/O requests may saturate the disk, (b) transactions hold locks while waiting for the log flush, (c) extensive context switching overwhelms the OS scheduler with threads executing log I/Os, and (d) contention appears as transactions serialize accesses to in-memory log data structures. We demonstrate these problems and address them with techniques that, when combined, comprise a holistic, scalable approach to logging. Our solution achieves a 20%-69% speedup over a modern database system when running log-intensive workloads, such as the TPC-B and TATP benchmarks. Moreover, it achieves log insert throughput over 1.8GB/s for small log records on a single socket server, an order of magnitude higher than the traditional way of accessing the log using a single mutex
Posted by Manos Athanassoulis at 16:46
DIAS blog first entry.

In this blog you can follow the news of DIAS lab.

Posted by Manos Athanassoulis at 15:13
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