I/O - IOmeter (Workload Generator)

> I/O - (Input/Output|Read/Write) - Data Access

1 - About

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

3 - Architecture

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).

4 - Glossary

4.1 - Manager

  • Each running copy of Dynamo is called a manager;

4.2 - Worker

  • 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.


5 - Measurement

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.

6 - Configuration

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.


6.1 - Disk


  • 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

7 - Steps

7.1 - Local

  • 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.

7.2 - Network

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

dynamo IOMeterHostNameMachine

7.3 - Command Line

iometer /c bigtest.icf /r bigtest_results.csv


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

8 - Documentation / Reference