case study: a database service
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Case Study: A Database Service. CSCI 8710 September 25, 2008. DB Server Log Sample. OS Performance Measurements. Basic Statistics for the DB Service Workload. Quantiles (quartiles, percentiles) and midhinge. Quartiles : split the data into quarters. - PowerPoint PPT PresentationTRANSCRIPT
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Case Study: A Database Service
CSCI 8710September 25, 2008
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DB Server Log Sample
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OS Performance Measurements
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Basic Statistics for the DB ServiceWorkload
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Quantiles (quartiles, percentiles) andmidhinge
• Quartiles: split the data into quarters.– First quartile (Q1): value of Xi such that 25% of the
observations are smaller than Xi.– Second quartile (Q2): value of Xi such that 50% of
the observations are smaller than Xi.– Third quartile (Q3): value of Xi such that 75% of
the observations are smaller than Xi.• Percentiles: split the data into hundredths.• Midhinge: (Q3 + Q1) /2
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Example of Quartiles
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Example of Percentile
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Range, Interquartile Range,Variance, and Standard Deviation
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Meanings of the Variance andStandard Deviation
• The larger the spread of the data around the mean, the larger the variance and standard deviation.
• If all observations are the same, the variance and standard deviation are zero.
• The variance and standard deviation cannot be negative.
• Variance is measured in the square of the units of the data.
• Standard deviation is measured in the same units as the data.
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Coefficient of Variation
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Box and Whisker Plots
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Total No. of I/Os vs CPU Time
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Result of Clustering Process
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QN for the DB Server
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Building a Performance Model
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CPU Apportionment Factor
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Disk 1 Apportionment Factor
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Disk 2 Apportionment Factor
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Model Parameters
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Using the Model
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Workload Intensity Variation
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Class 2 Response Time for VariousScenarios
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Monitoring Tools
• Hardware monitors• Software monitors– Accounting systems– Program analyzers
• Hybrid Monitors• Event-trace monitoring• Sample monitoring
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The Measurement Process
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Execution Environments forApplication Programs
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Execution Environments forApplication Programs
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Bare Machine Example
• Consider an early computer with no OS that executes one program at a time.
• During 1,800 sec, a hardware monitor measures a utilization of 40% for the CPU and 100 batch jobs are recorded. The average CPU demand for each job is:0.4 x 1800 / 100 = 7.2 seconds
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Execution Environments forApplication Programs
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OS Example
• Consider a computer system running batch programs and interactive commands. The system is monitored for 1,800 sec and a software monitor measures the CPU utilization as 60%. The accounting log of the OS records CPU times for batch and for the 1,200 executed interactive commands separately. From this data, the class utilizations are batch = 40% and interactive = 12%.
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OS Example (cont’d)
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Execution Environments forApplication Programs
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TP Example
• A mainframe processes 3 workload• classes:– batch (B), interactive (I), and transactions (T).
• Classes B and I run on top of the OS and class T runs on top of the TP monitor.
• There are two types of transactions: – query (Q) and update (U).
• What is the service demand of update transactions?
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TP Monitor Example
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TP Example (cont’d)
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TP Example (cont’d)
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Execution Environments forApplication Programs
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VM Example
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VM Example (cont’d)
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VM Example (cont’d)
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Computing the averageconcurrency level