DiskSim – Storage System Simulator
Michigan-CMU
Sriram Govindan
sgovinda@cse
Flow
Very simple process model
Application
file system (buffer cache)
IO-driver
bus
disk controller
disk cache
disk array
Simulated by
DiskSim
What is happening?
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Request flow through a series of storage components

We are interested in the time the request took in each such
component – model each component.
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Write equations for each component that captures its latency
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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/
characteristics (impact on each other)
●
●
workload/
software
Compare performance/fairness of different IO-Driver scheduling
algorithms.
Vary cache size/stripe units for workload and see its impact etc.
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,
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External I/O request trace.
Internally generated Synthetic workloads.
What it is not
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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.
Ok, now i want to work with DiskSim ?
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Sure..

Go to, http://www.pdl.cmu.edu/DiskSim/

Download DiskSim and Of course install it.
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
Older version of GCC ??
Help !!!
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download reference manual
Join DiskSim Mailing list
DiskSim files of interest
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Trace file

2, 8558368, 8192, R, 1533.481433

0, 23567168, 32768, R, 1533.482327
1, 19115920, 8192, R, 1533.974335



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websearch_trace
0, 32023120, 24576, R, 1533.974568
2, 25869888, 16384, R, 1533.979951
Disk specs
disk_specs
Parameter file
parameter_file
Output file
output_file
Running DiskSim
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DiskSim3.0 Reference manual – page 7, Section2.