vNUMA: A VMware Admin’s Guide

Since I’ve been discussing this recently at work with developers and managers due to some SQL Server issues we have been having, I decided it was time to write about it.  vNUMA was introduced along with vSphere 5 back in the day and is related to NUMA (Non Uniform Memory Architecture). In a nutshell, vNUMA allows you to divide your CPU and Memory resources into different nodes and allows for faster memory access.

vNUMAThe image above shows how NUMA breaks up the resources to create the nodes.  This is also a setting that can be controlled within VMware.  vNUMA is typically used for your “Monster VMs”, where your virtual CPUs span multiple physical CPUs. For example, if your virtual machine has 12 CPUs and your physical host has 8 cores, you are spanning multiple CPUs.  vNUMA is also recommended when using more than 8 vCPUs.  To change the NUMA setting (Keep in mind that the VM must be powered off to make this change):

  1. Select your VM
  2. Choose Edit Settings…
  3. Go to the Options tab
  4. Go to Advanced -> General
  5. Click the button “Configuration Parameters”
  6. Add the following “numa.vcpu.min” and set to the number of CPUs you want used in the NUMA node.

One thing to keep in mind with NUMA is that you want to size the NUMA nodes according to the number of cores in your physical host.  For example, my physical hosts have a six core processor, so my NUMA node on the SQL Server is set to 6.  This gives my 12 processor SQL Server 2 NUMA nodes with 6 CPUs each.  By default, when you create a VM with more than 8 vCPUs, vNUMA is enabled by default.  Using the instructions above, you can change the vNUMA value or set it on VMs with less than 8 vCPUs.

vNUMA is very specific to certain use cases and should be used with caution.  Incorrectly configuring NUMA can cause more problems than leaving it at the default.  Be sure to test your settings on a non production server and see if the results were as expected.  One final thought and last thing to keep in mind, ensure that the hosts in your cluster when vNUMA is being used have similar NUMA configurations to avoid issues when the VM decides to vMotion to a different host.

Image courtesy of


Script to Add Multiple NFS Datastores to an ESXi Host

I am sure I’m not the first admin that has needed to add an NFS datastore to multiple hosts, and usually it’s multiple datastores that are needed as well. Normally, I would go to each host, and add the storage manually via the vSphere Client.  But after doing this for quite some time, I decided I needed a better way to get this task done.  Scripting!

I have recently started to use PowerCLI to automate many of my daily tasks (Hint: more scripts to come) and decided to share the one I’ve used the most first.  The script takes an input after running, asking you to input your host name.  Inside the script, you will set the datastores you want to add to the host.  Those are the only changes that are needed when being run.  This script has saved me a great deal of man hours and some headaches.  A great advantage to scripting is that you avoid those sneaky spelling mistakes or clicking the wrong button.

The script is below here (The bold parts are what need to be changed by you):

$VMHost = (Read-Host “Please enter the name of your ESX Host you wish to configure”)

$shellObject = new-object -comobject
$intAnswer = $shellObject.popup(“Do you want to add the datastores?”, 0,”Add datastores – remember you must have added the hosts on the storage”,4)
If ($intAnswer -eq 6) {
Write “Creating Datastores on $VMHost…”
New-Datastore -Nfs -VMHost $VMHost -Name DatastoreName1 -Path /vol/DatastoreName1 -NfsHost
New-Datastore -Nfs -VMHost $VMHost -Name DatastoreName2 -Path /vol/DatastoreName2 -NfsHost
New-Datastore -Nfs -VMHost $VMHost -Name DatastoreName3 -Path /vol/DatastoreName3 -NfsHost
} else {
Write “Skipping Datastores on $VMHost…”

When running the script, you will see the following output asking you to put in your hostname:


You will then see a successful message for each datastore added to the host. You must remember to add the host to the NFS Export share on the storage itself before completing this step.

Script courtesy of VMware PowerCLI Blog

VMware releases vCenter Server 5.1 Update 1a


VMware released vCenter Server 5.1 Update 1a on May 22nd in reply to a known issue that users were seeing related to logging into vCenter.  Users that had a large number of AD groups in their environment would see an error when logging in using SSO.  This issue has been fixed in Update 1a and some other improvements were snuck in as well:

  • vCenter server can now run on Windows Server 2012
  • vCenter not supports SQL Server 2008 R2 and SQL Server 2012
  • You can now customize the following Guest OS’s: Windows 8, Windows Server 2012, RHEL 5.9 and Ubuntu 12.04
  • The vRAM limit of 192GB has been removed
  • And other bug fixes

The upgrade and installation process is the same as previous releases.  You can do an in place upgrade from 4.x and up or you can always do a new install.  And remember that all the new features within vCenter can only be accessed through the web client, so ditch the desktop client and fully utilize your vCenter.

You can read the full version of VMware’s release notes for vCenter server 5.1u1a here.

New Blogger, Virtual Champion

After over 7 years in the IT business, I felt it appropriate to start my own blog to store my ideas and problems that I run into during my work.  This will be my place to share knowledge with the world and others in the IT industry.  I hope this blog will help you and I will continue to update content regularly with tips, how-to’s and news in the virtual world.