DiskSim

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DiskSim Storage System SimulatorMichigan-CMU

• Sriram Govindan
• sgovinda_at_cse

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Flow

• Application
• file system (buffer cache)
• IO-driver
• bus
• disk controller
• disk cache
• disk array

Very simple process model
Simulated by DiskSim
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What is happening?

• Request flow through a series of storage
  components
• We are interested in the time the request took in
  each such component model each component.
• Write equations for each component that captures
  its latency
• eg. equation to calculate seek time, given
  current head position, cylinder to seek etc.
  (separate equations for barracuda disk and
  Seagate disk - obtained through
  micro-benchmarks),
• eg. constants for other models (bus
  arbitration).
• Capture dependency among request.
• We are also interested in component/ workload/
  software characteristics (impact on each other)
• Compare performance/fairness of different
  IO-Driver scheduling algorithms.
• Vary cache size/stripe units for workload and see
  its impact etc.

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What it is

• Highly accurate and widely used.
• Open Source, written in C - what else v need?
  -)
• Easily attach to a full system simulator.
• Driven by,
• External I/O request trace.
• Internally generated Synthetic workloads.

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What it is not

• Cannot model interactions with other system
  components, unless integrated with an accurate
  full system simulator.
• CPU Scheduler effects.
• Other components competing for BUS etc.
• Work with numbers and not with data, Of course.

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Ok, now i want to work with DiskSim ?

• Sure..
• Go to, http//www.pdl.cmu.edu/DiskSim/
• Download DiskSim and Of course install it.
• Older version of GCC ??
• Help !!!
• download reference manual
• Join DiskSim Mailing list

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DiskSim files of interest

• Trace file websearch_trace
• 2, 8558368, 8192, R, 1533.481433
• 0, 23567168, 32768, R, 1533.482327
• 1, 19115920, 8192, R, 1533.974335
• 0, 32023120, 24576, R, 1533.974568
• 2, 25869888, 16384, R, 1533.979951
• Disk specs disk_specs
• Parameter file parameter_file
• Output file output_file

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Running DiskSim

• DiskSim3.0 Reference manual page 7, Section2.

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