I/O - IOmeter (Workload Generator)

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IOmeter is a disk-testing, IO workload generator tool which generate and measure storage performance.

Iometer is pronounced “eye-OM-i-ter,” to rhyme with “thermometer.” Iometer does for a computer’s I/O subsystem what a dynamometer does for an engine: it measures performance under a controlled load. Iometer was formerly known as “Intel's Galileo”.

It can be configured to emulate:

  • disk
  • or network I/O load


Iometer consists of two programs:

  • Iometer (the GUI administration tool)
  • and Dynamo. (the multithreaded workload generator)

Iometer is both:

  • a workload generator (that is, it performs I/O operations in order to stress the system)
  • and a measurement tool (that is, it examines and records the performance of its I/O operations and their impact on the system).

If you want to run Dynamo on multiple machines, Dynamo.exe must be available on each machine (on either a local or networked disk).



  • Each running copy of Dynamo is called a manager;


  • each thread within a copy of Dynamo is called a worker.

Intel recommends to create one worker per processor. They receives their I/O Access Pattern.


It can measure not only the throughput, but provides a wealth of information about the system utilization and latency.

Iometer can be used for measurement and characterization of:

  • Performance of disk and network controllers.
  • Bandwidth and latency capabilities of buses.
  • Network throughput to attached drives.
  • Shared bus performance.
  • System-level hard drive performance.
  • System-level network performance.


It can be configured to emulate the disk or network I/O load of any program or benchmark, or can be used to generate entirely synthetic I/O loads. It can generate and measure loads on single or multiple (networked) systems.

An access pattern contains mainly the following parameters:

  • Transfer Request Size - a minimal data unit to which the test can apply.
  • Percent Random/Sequential Distribution - percentage of random requests to set the access mode (random or sequential)
  • Percent Read/Write Distribution - percentage of requests for reading.

Another important variable which is not directly included into the access pattern - # of Outstanding I/Os - defines a number of simultaneous I/O requests for the given worker and, correspondingly, disc load.



  • Blue icons represent physical drives; they are only shown if they have no partitions on them.
  • Yellow icons represent logical (mounted) drives; they are only shown if they are writable.
  • A yellow icon with a red slash through it means that the drive needs to be prepared before the test starts



  • Open iometer.exe (It will start one copy of Dynamo on the same machine)
  • Select a worker
  • Select a disk for the worker
  • Select an access specification for the workers
  • Select more worker and do it again if needed
  • Start the workload with the green flag
  • Go to the Results Display tab
  • Set the Update Frequency (seconds) to five to see live the results.


On each machine, start dynamo by giving the name of the machine running Iometer

dynamo IOMeterHostNameMachine

Command Line

iometer /c bigtest.icf /r bigtest_results.csv


  • bigtest.icf is a IOMeter config file
  • bigtest_results.csv is the result

Documentation / Reference

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