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Systems Engineering 1 -- Assignment 1 -- Cold storage Modeling

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I. Task:

A. Task description:

Model using PRISM tool a file stored persistently by sharding it between 4 data centers using 3/4 coding and each shard should be stored locally in each datacenter sharded using 17/20 coding.

Hint-- the file is not replicated and only one copy exists.

Hint-- the file is durable if maximum one data center fails --> (failedDC<=1)

B. Model inputs:

Datacenter:

• fails at rate of dcFR = 0.01%
• repairs at rate of dcRR.

Disk:

• fails at rate of diskFR = 5%.
• repairs at rate of diskRR.

Time frame = 1 year

C. Task requirement:

Calculate the file availability i.e., the probability that the file will survive one year, if the repair rates for disks and dc are respectively:

• 1 week, 1 week
• 1 week, 1 day
• 1 day, 1 week
• 1 day, 1 day.

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II. Required Files List:

• model.prism > the ctmc model code
• props.csl > the property to calculate the availability
• ctmc.pdf > the ctmc state diagram
• 1d1d.txt > availability when diskRR=1 day and dcRR=1 day
• 1d1w.txt > availability when diskRR=1 day and dcRR=1 week
• 1w1d.txt > availability when diskRR=1 week and dcRR=1 day
• 1w1w.txt > availability when diskRR=1 week and dcRR=1 week

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III. Reference Slides:

https://tu-dresden.de/ing/informatik/sya/se/ressourcen/dateien/teaching/courses/ws/systems_engineering_1/winter-semester-2018/exercises/SE1-2018-E5-CSA.pdf?lang=en

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IV. Prerequisites:

• windows/linux/Mac
• Java7
• c/c++ compiler

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V. PRISM Installation:

http://www.prismmodelchecker.org/manual/InstallingPRISM/Instructions

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VI. Submission Instructions:

• Use the empty files provided in the repository to include you solution--> do not change the names of files.
• Deadline: 09.12.2018--no submission will be accepted after that.

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VII. Questions:

SE1 auditorium: https://auditorium.inf.tu-dresden.de/en/groups/110631001