City Research Online City, University of London Institutional Repository Citation: Stankovic, V. (2008). Performance Implications of Using Diverse Redundancy for Database Replication. (Unpublished Doctoral thesis, City, University of London) This is the accepted version of the paper. This version of the publication may differ from the final published version. Permanent repository link: https://openaccess.city.ac.uk/id/eprint/17440/ Link to published version: Copyright: City Research Online aims to make research outputs of City, University of London available to a wider audience. Copyright and Moral Rights remain with the author(s) and/or copyright holders. URLs from City Research Online may be freely distributed and linked to. Reuse: Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. City Research Online: http://openaccess.city.ac.uk/ [email protected] Performance Implications of Using Diverse Redundancy for Database Replication by Vladimir Stankovic [email protected] Centre for Software Reliability City University London EC1V 0HB United Kingdom February 2008 List of Contents 1. Introduction..............................................................................................................1 1.1. Motivations and Aims.........................................................................................1 1.2. Summary of Work...............................................................................................3 1.3. Thesis Outline .....................................................................................................5 2. Concepts and Background ......................................................................................6 2.1. Fault Tolerance via Diverse Redundancy ...........................................................6 2.2. Database Definitions ...........................................................................................9 2.2.1. Transactions .................................................................................................9 2.2.2. Isolation Levels ..........................................................................................11 2.2.3. Concurrency Control and Correctness Criteria..........................................13 2.2.4. Liveness......................................................................................................16 2.3. Database Replication.........................................................................................17 2.3.1. ROWAA-Based Replication ......................................................................18 2.3.2. Correctness in Replicated Databases .........................................................19 2.3.3. Conflicts and Deadlocks ............................................................................23 2.3.4. Transaction Atomicity................................................................................24 2.4. TPC-C – an On-Line Transaction Processing Benchmark ...............................25 3. Architecture of DivRep Middleware ....................................................................28 3.1. DivRep – Replication with Diverse Database Servers......................................28 3.1.1. Dependable Replication Algorithm (DRA) ...............................................32 3.1.2. DRA Optimisations....................................................................................40 3.1.3. Distributed Deadlock Avoidance ...............................................................42 3.2. Correctness of DRA ..........................................................................................46 3.2.1. Safety .........................................................................................................46 3.2.2. Liveness......................................................................................................48 3.3. Hybrid Approach of DivRep.............................................................................49 3.4. Discussion .........................................................................................................50 3.4.1. Comparing DivRep to Other Replication Techniques ...............................51 3.4.2. Possible Changes to DivRep ......................................................................53 4. Experimental Evaluation of DivRep Performance .............................................56 4.1. Test Harness......................................................................................................57 iii 4.2. Preliminary Experiments – Systematic Differences in the Performance of Diverse Servers........................................................................................................64 4.3. When Diverse Redundancy Performs Better than Non-Diverse Redundancy .68 4.3.1. Confidence in the Results ..........................................................................70 4.3.2. Performance Comparison of Different DBMS Configurations .................70 4.4. Performance Implications of Improving Dependability ...................................74 4.4.1. SI-Rep Simulation .....................................................................................75 4.4.2. DivRep vs. a ROWA-Based Replication (SimSI-Rep) .............................76 4.4.3. Discussion of DivRep vs. SimSI-Rep Comparison ...................................84 4.4.4. User-Centric Analysis................................................................................86 4.5. Minimising Replication Overhead Using Priority Mechanisms.....................100 4.5.1. The Problem.............................................................................................100 4.5.2. The Solution.............................................................................................103 4.5.3. Discussion................................................................................................107 4.5.4. Related Work ...........................................................................................110 5. Uncertainty-Explicit Assessment of DivRep Components...............................111 5.1. Motivation for Using Uncertainty-Explicit Assessment.................................112 5.2. Bayesian Approach to Assessment of a Single Attribute ...............................114 5.3. A Model for Assessment of 2 Non-Independent Attributes ...........................115 5.4. A Numerical Example ....................................................................................117 5.4.1. Prior Distributions ...................................................................................119 5.4.2. Observations ............................................................................................120 5.4.3. Posteriors .................................................................................................121 5.5. Discussion and Related Work.........................................................................123 6. Related Work .......................................................................................................126 6.1. A Multitude of Database Replication Solutions .............................................126 6.2. Load Balancing and Adaptability ...................................................................130 6.3. Consistency Guarantees..................................................................................133 7. Conclusions...........................................................................................................135 7.1. Research Assessment......................................................................................136 7.2. Future Directions ............................................................................................138 Bibliography.............................................................................................................141 List of Acronyms......................................................................................................152 Appendix A...............................................................................................................153 iv Database Schema of the Log Database ..................................................................153 v List of Tables TABLE 4-1 ..............................................................................................................................80 TABLE 4-2 ..............................................................................................................................81 TABLE 4-3 ..............................................................................................................................91 TABLE 4-4 ..............................................................................................................................91 TABLE 4-5 . ............................................................................................................................99 TABLE 4-6 ............................................................................................................................107 TABLE 5-1 ............................................................................................................................116 TABLE 5-2 ............................................................................................................................120