Cooperative scans: dynamic bandwidth sharing in a DBMS

  • Authors:

  • Marcin Zukowski;Sándor Héman;Niels Nes;Peter Boncz

  • Affiliations:

  • Centrum voor Wiskunde en Informatica, SJ Amsterdam, The Netherlands;Centrum voor Wiskunde en Informatica, SJ Amsterdam, The Netherlands;Centrum voor Wiskunde en Informatica, SJ Amsterdam, The Netherlands;Centrum voor Wiskunde en Informatica, SJ Amsterdam, The Netherlands

  • Venue:
  • VLDB '07 Proceedings of the 33rd international conference on Very large data bases
  • Year:
  • 2007

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Abstract

This paper analyzes the performance of concurrent (index) scan operations in both record (NSM/PAX) and column (DSM) disk storage models and shows that existing scheduling policies do not fully exploit data-sharing opportunities and therefore result in poor disk bandwidth utilization. We propose the Cooperative Scans framework that enhances performance in such scenarios by improving data-sharing between concurrent scans. It performs dynamic scheduling of queries and their data requests, taking into account the current system situation. We first present results on top of an NSM/PAX storage layout, showing that it achieves significant performance improvements over traditional policies in terms of both the number of I/Os and overall execution time, as well as latency of individual queries. We provide benchmarks with varying system parameters, data sizes and query loads to confirm the improvement occurs in a wide range of scenarios. Then we extend our proposal to a more complicated DSM scenario, discussing numerous problems related to the two-dimensional nature of disk scheduling in column stores.