From IOmeter to VMware I/O Analyzer fling

by Nov 9, 2016VMware, vSAN, vSphere

Reading Time: 6 minutes

VMware I/O Analyzer is a tool to launch orchestrated tests against a storage solution available from the VMware flings website. It can be used as a single appliance where the worker process and the analytics is done within. Additional appliances can be deployed to act as Worker VMs. The Analyzer VM launches IOmeter tests (on the Worker VMs) and after test completion it collects the data. All configuration is done from a web interface on the Analyzer VM.

This post is describing how I deployed VMware I/O Analyzer and how I got to a test with maximized IOs. The first tests were conducted launching a IOmeter from within a virtual machine on the vSAN datastore and showed more or less 300 IOs being generated. In the end 18 Worker VMs with 8 disks each on a 6 host vSAN cluster were used generating 340K+ IOPS. The purpose was to create a baseline for a VSAN datastore maximum IOPs.

Hardware used

6 hosts
1 disk group
1 800GB SSD drive5 1,2 TB 10K SAS
vSphere 5.5 U3


The VM OS disks should not be put on the vSAN datastore you want to test, if not the generated IOPs will be part of your report. To keep the Analyser VM IOPS out of the performance graphs, put it on a different datastore.

Deploy one Analyser VM. Deploy a Worker VM per ESXi host. You should end up with as much Worker VMs as you have hosts in your cluster.

I changed the IP of all VMs to static as there was no DHCP server available in the subnet. This means that no DNS entries were required.

Preferably you will want to change the Analyser VM to a static IP as you will manage the solution from a web browser. The Worker VMs you can leave as is if there is DHCP server available. You will need dns entries and change the configuration used here.

To work easily set the Worker VMs on static IPs or create dns aliases as you will be doing a lot of work on the Worker VMs. I prefer static IPs because they add no complexity due to name resolving, etc…


Download ova from:


Deploying the Analyser VM:

Deploy ovf template. Choose your settings in regards to the recommendations above.

Delete the 100MB disk (second disk) from the virtual machine.

Start the Analyser VM via vSphere client and the open console

Login with root – vmware

A terminal window will be opened upon login

To configure static IP:

Change /etc/sysconfig/network/ifcfg-eth0 with your preferred text editor.

Assuming the subnet you’re deploying the vm is

Change the following lines highlighted to your needs:

Leave the other lines as is.

Save and close the file (:wq)

Now we will configure the default gateway

Assuming your default gateway is

Add / Change the following line:

Save and close the file (:wq)

Restart the network service:

Check if the VM is reachable.

Now shutdown the VM.

Deploying the Worker VM:

Clone the Analyser VM.

Add a Hard Disk of 1GB.

Choose advanced and put the 1GB disk on the VSAN datastore.

I needed to configure static IPs on the Worker VMs, so I had to start each VM and change the IP address. After changing the network settings, shut down the VM and create a new clone. Not changing the IPs will give duplicate IPs.

Ease of access configuration

Two ease of access configurations were applied. The first is configured for easy copying from the Analyzer VM to the Worker VMs. The second because all appliances need to be logged onto for the VMware IO Analyzer solution to work. All commands are executed on the Analyzer VM and then copied to the Worker VMs.

Setup ssh keyless authentication

Generate a key pair

ssh-copy-id will copy your public key to the target machine

The root account password of the destination will need to be supplied for each of the above lines.

BE AWARE: This has the following security downside. If the root account is compromised on the Analyzer vm all worker vms should be considered compromised too.


Change autologon=”” to autologon=”root” in the displaymanager (/etc/sysconfig/displaymanager) file with the following command:

This will force the machine to login with root after boot.

Copy the file to all workers:

Affinity rules

TIP: Create affinity rules in vCenter to keep the Worker VMs on dedicated hosts, otherwise the configuration on the VMware I/O Analyzer dashboard will be outdated soon. The consequence is that certain Worker VMs will not be launching their IOmeter profiles and therefor the reports will not be correct.



Enable the SSH service on the ESXi hosts via the vSphere (Web) Client or through Powershell.

The powershell way: (be aware to filter your hosts if needed). There is a dedicated post about starting and stopping ESXi services through powershell here.


Add the hosts to the host list.

Search for the Worker VMs in the list and add preferred IO test.

There are a lot of standard tests included in the appliance. The one that should be generating the most IOPs is 4k, 100% read and 0% random.

Optimized setup

To reach an optimized setup, three Worker VMs per host were deployed and 7 additional disks were added.

Adding the extra disks via PowerCLI:

The following specification was created on the Analyzer VM…

… and copied over to the Worker VMs


I found that looking at the console of the Worker VMs is interesting for troubleshooting. You can see the IOmeter tests being launched. This was very usefull in the process of creating the IOmeter profile. You don’t need to wait untill the test is finished to see it has failed. Stopping IOmeter tests from the console gives the opportunity to look at, edit and save the launched profile.

Harold Preyers

Harold Preyers

Solution Architect

VMware Certified Advanced Professional - Network Virtualization Design 2021