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Planning DB Service Level Agreements with Stochastic Petri Nets

A simulation model based on stochastic Petri nets to estimate the performance of DB transactions for negotiating appropriate SLAs.

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Planning DB Service Level Agreements with Stochastic Petri Nets

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  1. Planning Databases Service Level Agreements through Stochastic Petri Nets M. Teixeira and Pablo Sabadin mt@das.ufsc.br, pablo@duetotecnologia,com.br 1

  2. Motivation  The SOA has became a pattern for planning business transactions in distributed environments; Proposal:  In SOA, the requirements are expressed by SLA One kind of clauses is regarding to DB operations A Simulation modeling approach, based on stochastic Petri nets, to estimate the performance of DB transactions PROBLEM:  It is very difficult negociating an appropriated SLA, that could be guaranteed in practice! Performance Estimation 2 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  3. Presentation Outline  Preliminaries:  Proposed Model  SOA  Context  Structure  Notation Involved concepts Context of the problem Motivation  Exemplo Process Defined SLA clauses Input Parameters PMF  Simulations Petri nets Involved concepts  Conclusions 3 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  4. SOA Context  Goal Business process integration.  Features Functionality as services;  Distributed;  Orchestrated.  Main advantages:  Flexibility; Interoperability; Reuse; ... 4 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  5. SOA Transaction Orchestration DB Assign WS 1 Invoker Requestor WS 2 Reply DB 5 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  6. Server 2 Server 1 Capacity Planning system crash Server 3 6 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  7. Proposed Model - Context Teixeira et al. 2009, 2010, 2011 SBBD proposal Rud et al. 2006, 2008 Wu et al. 2008 7 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  8. Proposed Model - Structure ResponseTime = E{#P_Stat}*Delay <---- 8 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  9. Proposed Model - Feeding dli = delay Workload = 1/delay Ri = Memory Pages (Number * Size) Ki = Supported parallel DB operations (Measured) Arcs = Size of the exchanged messages (Measured) 9 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  10. Proposed Model - Feeding Jain, 1991 m = average s = stardard Deviation s/m > 1 (Hyper-Exponential) s/m = 1 (Exponential) . . . . Desrochers, 1994 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11 . . 10

  11. Case Study - Process 11 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  12. Case Study – Measured Parameters Example of a DB request. Implement a query that returns all the clients and their respective negotiated invoices, admitting that: (i) the merchandises were already shipped; (ii) the deadline for the payment is in, at most, one month. Sort the results by the invoice deadline. 12 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  13. Case Study – PMF Adoption  36  Average: ms   17   Std. Deviation: ms  17   , 0 47   Coefficient of Variation:  36 Hypo-Exponential  2  23 3  d 1 12  d  13 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  14. Entire Model Hypo-Exponential 14 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  15. Case Study – Simulations and Results 83% 15 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  16. Case Study – SLA Planning Question 1: Let W be a predefined workload of requests arriving at DB server (req/sec). Which SLA, for the DB mean response time, could be guaranteed in practice? Alternative 1: For W = 5 SLA ≈ 0,4 s Alternative 3: For W = 50 SLA ≈ 4 s Alternative 2: For W = 10 SLA ≈ 1 s 16 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  17. Case Study – SLA Planning Question 2: Let RT be an established SLA for the response time. Which SLA, for the higher supported workload, could be guaranteed in practice, such that the mentioned RT is not exceeded? Alternative 1: For RT = 0,5 s Alternative 3: For RT = 3 s Alternative 2: For RT = 1 s SLA ≈ 10 req/sec SLA ≈ 40 req/sec SLA ≈ 6 req/sec 17 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  18. Closing Remarks  We proposed a simple and flexible model;  We based on a real lack observed in the industry  The work was not conceived to be only a theoretical idea  Plans for the future:  Extending the performance model  Embodying a failure model  Improving the model validation  Estimating metrics for very large databases  Using the model in practice 18 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

  19. Acknowledgments Thank you all! I'm available for questions. 19 Planning Databases Service Level Agreements through Stochastic Petri Nets – SBBD’11

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