What is ESXi Quick Boot?

Just think about your patch management process. You may need to reboot your ESXi hosts during the process. Host reboots may not be performed frequently and not all patches require host to be rebooted. However, when activities such as critical patch or driver installation are performed, we may have to reboot the host.

Now the question is, how much time does it takes for a host reboot cycle to complete? Also at what stage, large amount time is spent in host boot process?

Server hardware available these days support heavy configurations such as large amounts of memory due to which server reboots may take few minutes to perform firmware and hardware device initializations (POST).

That brings up another question here, do we really have to perform these hardware initialisations every time we reboot a host considering that it was already initialized when server got powered on initially? In other words, can’t we simply reboot just the software part (Hypervisor in this case)?

This is where vSphere Quick Boot comes to our rescue and does exactly just that.

Quick Boot functionality allows restarting only the hypervisor instead of going through a full reboot of the host hardware including POST process. This feature is used with vSphere Update Manager during patching and upgrade process. Quick boot helps to complete maintainance activities more quickly.

Quick Boot eliminates the time-consuming process of hardware initialization by shutting down hypervisor and then immediately re-starting it. So basically we skip the firmware and hardware initialisation process completely when using Quick Boot feature. Update manager as we all know, puts one host into maintenance at a time by default (this behaviour can be changed though). In large clusters, vSphere quick boot functionality substantially reduces timeframe required for maintenance windows.

How to enable quick boot?

We need to enable quick boot functionality through Update manager as shown below.

On update manager page, navigate to settings, select hosts and click edit

Put check mark infront of enable quick boot option.

Here is a demo on vSphere quick boot by VMware that shows the performance difference between quick boot and regular reboot .

Before you go ahead and try using quick boot, there are prerequisites to it. Not all server hardware configurations support the Quick Boot feature. Quick boot runs only on supported hardware.

To check if your system is compatible with Quick Boot, run this command on the ESXi host from the shell:


Below are examples of Power Edge servers from Dell where quick boot is supported.

  • PowerEdge R740
  • PowerEdge R740xd
  • PowerEdge R640
  • PowerEdge R730
  • PowerEdge R730xd
  • PowerEdge R630

For more information on supported hardware from different vendors check below links

The QuickBoot feature also includes pre-checks functionality to prevent the usage on an unsupported configuration. If any of these pre-check are not met, a regular reboot is performed instead. For more detail on requirements and constraints, check VMware KB article 52477

Another prerequisite is that Quick boot functionality is only available for ESXi hosts that are running ESXi 6.7 and later. So even if your hardware is compatible, if you are running a legacy version, quick boot feature will not be available until you upgrade to 6.7. For ESXi 7.0, if the script returns that your system is compatible, you should check the server vendor documentation for any additional restrictions.

Cheers!!! Hope its informative

If you liked it, do comment, like, and share.

Leave a Reply