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I/O Analyzer

I/O Analyzer


VMware I/O Analyzer is an integrated framework designed to measure storage performance in a virtual environment and to help diagnose storage performance concerns. I/O Analyzer, supplied as an easy-to-deploy virtual appliance, automates storage performance analysis through a unified interface that can be used to configure and deploy storage tests and view graphical results for those tests.

I/O Analyzer can use Iometer to generate synthetic I/O loads or a trace replay tool to deploy real application workloads. It uses the VMware VI SDK to remotely collect storage performance statistics from VMware ESX/ESXi hosts. Standardizing load generation and statistics collection allows users and VMware engineers to have a high level of confidence in the data collected.

Please post comments and questions regarding this fling to the I/O Analyzer Community.


  • Integrated framework for storage performance testing
  • Readily deployable virtual appliance
  • Easy configuration and launch of storage I/O tests on one or more hosts
  • Integrated performance results at both guest and host levels
  • Storage I/O trace replay as an additional workload generator
  • Ability to upload storage I/O traces for automatic extraction of vital metrics
  • Graphical visualization of workload metrics and performance results

New in version 1.6.2

  • Patched BASH binary to fix Shellshock vulnerability
  • Patched OpenSSL library to fix Heartbleed vulnerability
  • Added warning messages when invalid VM names are detected

You can also grab the tarball vmware-io-analyzer-1.6-vmw.oss.tgz

System Requirements

I/O Analyzer has the following minimum system requirements:

  • VMware ESX/ESXi version 4.0 or later
  • 16.5 GB of storage space (additional space recommended)
  • 1 vCPU and 2048 MB VM memory
  • A supported Internet browser (Google Chrome or Mozilla Firefox)


Complete installation and usage instructions are included in the VMware I/O Analyzer Installation and User’s Guide.



Change Log


Jinpyo Kim

VMware Performance

Chien-Chia Chen

VMware Performance

Sankaran Sivathanu

VMware Performance
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31 thoughts on “I/O Analyzer

  1. Tom Miller

    Thanks guys. What an awesome tool. Ran it against a 4 drive array and a 2 drive array and can really see the difference. I’ve always wanted to use iometer, now I can with pre-configed models.

  2. Jinpyo Kim

    Some people have deployed setup running real applications. They may want to collect esxtop for some performance analysis.
    In such use case, please add hostname and credentials. And run without specifying workload specifications.
    Then goto Results tab and select right result. You can quick check I/O stats. If you want to do further analysis, please click “Download Results” button and download .tgz file into your local machine.

    In Flings, we can find “esxplot” (https://labs.vmware.com/flings/esxplot) to browse through esxtop results.

  3. Jinpyo Kim

    * Internet browser to use: MS IE not supported, The Firefox and Chrome browsers are tested. Chrome is preferred.

    * Pulling vm lists properly: It took several seconds to pull vm list from a selected host. So select hostname and wait a few seconds and click “Refresh” button in browser. Then you can pull vm name list properly. The vm name is not important in actual operation, only for easier reading of results. But IP address of VM should be accurate to get proper test result.

    * Login requirement for each VM: in order to proper test, you should login VM first. (default login and passwd are in README file)

  4. Scot

    On the results page I am getting host results but no guest results ? Am i selecting the wrong workload spec ?
    I am interested in getting max IOPS from a guest and selecting the Max_IOPS.icf but those results are not showing up ?

    1. Jinpyo Kim

      Please sure that you put right IP address of VM in workload setup.
      You can check console window if Iometer is invoked properly or not.

      1. Scot

        The IP is correct I have tried a few VM’s. I went to check the console screen and it is completely grey ? Nothing is showing on any of the workspaces ?

          1. Jinpyo Kim

            Yes, it is ready to use. Now you can use Web UI for the test. If you want to Iometer from console, please right click of your mouse and open xterm. and run Iometer as described in totorial.pdf in zip file.

    1. Brad Clemmons

      Select the VM name you used when you imported the OVF. If you did not change the name it should read:
      vmware-io-analyzer-1.0.0 possibly ending with -t1, and be at the bottom of the list.

      1. jahansen

        I didn’t find the pdf at first… In the list of VMs there were several machine named something with ioanalyzer. I can send you a screenshot if I’m able to regenerate,


        1. Gabriel Chapman

          I’m guessing that, the list that is pre-populated is from the OVF when it was created and that someone did not clear out the VM’s listed from the host they were working on. Those VM’s do not exist, and you cannot run any tests with them. The drop down list should be the list of VM’s on the host you are connecting to.

  5. Constantin

    in my case the webserver does not come up.

    root@dhcp-10-0-100-217:/etc/init.d# ./vami-lighttp restart
    Shutting down vami-lighttpd: done.
    Starting vami-lighttpd: 2011-12-08 07:37:28: (/build/mts/release/bora-185256/vadk/src/vami/apps/lighttpd/1.5.0-2349/src/network.c.492) SSL: error:00000000:lib(0):func(0):reason(0)

    Any ideas?

    1. Jinpyo Kim

      Thanks Gabriel for your posting. We will really appreciate your comments on this tool. This tool was designed to minimize burdens and mistakes in I/O benchmarking and basic I/O performance trouble-shooting in virtualized environments. I will be very happy to hear back from many test cases.

    2. Jinpyo Kim

      I confirmed misalignment issue in guest I/O summary page.

      Until we revised appliance, here is a quick fix for it.

      Please edit the following line in /var/www/results/index.php file.

      line # 226: $linenum++ –> move after following if(), move it to line #234.
      line # 227: if (($linenum % 10) == 0) { –> if( ($linenum !=0) && ($linenum % 9) ==0 ) {

      It will fix misalign problem.

  6. Scot

    In the setup and run tab I add the host name and root password and it does nothing when i clcik add host. All i get is error on page ? Any advice am i doing something wrong ?

    1. Jinpyo Kim

      We have a problem with MS explorer browser. Firefox and Chrome will work fine. Chrome browser is actually recommended.

      1. Romx

        Since recent MSIE conform now latest web standarts, this incompatibility looks like your issue with following of web standarts. It will be great to avoid soon any ‘recommended web browser’ definitions.

    1. Jinpyo Kim

      It seems I/O Analyzer VM cannot talk to ESX host. Please check dns name of ESX host is resolved properly in VM. You may consider using ip address instead.

      If you can ping ESX host from your I/O Anlayzer VM, your password of ESX host may have special characters.
      We have a bug in handling special character in passwd of ESX host. If you add “\” in front of special character, it will work correctly. (for example, pa$$word should be typed line pa\$\$word in Web UI.

  7. Jim Moyle

    I had a look at the Workstation workload icf file that has been created for the io analyzer appliance and it seems to be 8k blocks, 80% read and 80% random.

    This seems to be much more a x64 server workload than an x86 Client workstation workload.

    It should be 4k blocks and 80% write for Workstation.

    Please see ProjectVRC and Win 7IOPS for details.



    1. Jinpyo Kim

      Thanks for the comments.

      We will add different workstation workload I/O profile.
      You can change/add I/O profile if you want to test different I/O profile using Iometer or text editor.

      If you log in VM, you check /var/www/configs to edit existing profile. If you add profile in /var/www/configs and add description of workload in /var/www/configs/icfDescriptions.txt, it will show up in Web UI.

  8. Gabriel Chapman

    The PDF doesn’t have the needed step of adding the additional disk (its listed in the read-me though). Without the additional disk, the IOMeter script doesn’t kick off properly in the VM.

    1. Jinpyo Kim

      Thanks for the comments.

      We added default 100MB virtual disk (for the test) in the appliance.
      For your initial sanity test, you can use provisioned default 100MB virtual disk.

      But for real performance test, please remove default 100MB virtual disk and add virtual disk with vSphere Client.
      We recommend using RDMp and eager-zeroed thick virtual disk for performance test.

      When you create virtual disk through vSphere Client, ESX creates lazy-zeroed thick disk as a default.
      But for proper performance test, we recommend using eager-zeroed thick disk.

      You can create eager-zeroed thick disk with the following cmds.
      $vmkfstools -c 10G -d eagerzeroedthick foo.vmdk

      In order to create

    1. Jinpyo Kim

      It supports ESX 4.0 and 4.1. It was tested with ESX 5.0 too.
      It was configured with LSI Parallel vHBA for broader compatibility, but LSI sas vHBA is more preferred.

      Since it generates I/Os from Linux guest OS, it is OK to use for SAN and NAS datastore.
      But since NAS is inherently thin-provisioned, you should consider it when you interpret the performance results.

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