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If we say that a cold reboot with POST is a traditional reboot, a warm reboot is VMware Quick Boot, with some "secret sauce" in between. VMware Quick Boot is especially useful in conjunction with vSphere Update Manager (VUM) to complete patching and upgrades much more quickly because the host does not go through all of the hardware initialization phases.
- VMware vSphere 6.7
- Supported hardware
Both requirements are hard requirements. This means this feature is only available for hosts running ESXi 6.7 or higher with supported hardware.
If you have newer hardware compatible with VMware Quick Boot, but you did not update your ESXi version, it won't work.
How can I make sure my hardware is compatible? ^
A small script allows you to test whether your hardware supports Quick Boot. Head over to the following knowledge base article at VMware.
You only have to connect to the console and run a single line of code since this script is part of ESXi 6.7 already. In my example, I'll show an incompatible host.
What are the constraints and requirements for Quick Boot? ^
Host platform is unsupported: One of the first constraints is there's no support for a host platform. In such a case, there is nothing you can do about it. Perhaps a future BIOS upgrade from your hardware manufacturer will allow Quick Boot, but nothing is certain.
Host is not configured to use a Trusted Platform Module (TPM): You cannot have a TPM and Quick Boot active at the same time.
Passthrough devices: Another constraint is you can't use Quick Boot with any passthrough devices configured for VMs on your host.
- No vmklinux drivers loaded on your host
- No other non-certified drivers loaded on your host
- Quick Boot is disabled in the Update Manager—you can easily check this in the UI (for now through the Flash-based web client only)
The idea from VMware is great, and it can make you save a lot of time when patching VMware infrastructures because many servers can spend significant time during POST.
When using a VMware virtual storage area network (vSAN), it's imperative to follow the hardware compatibility list (HCL) to ensure you have a supported firmware/driver combination. If you have an unsupported configuration, you might have problems. Even if your hardware is compatible with Quick Boot, the server might "freeze" with the error message "LoadESX in progress" during the boot process.
Where do you enable Quick Boot? ^
For now, the only way to enable Quick Boot is to use the Flash-based vSphere Web Client. This is a minor drawback at the moment. It seems this is one last part of the UI that needs to transition to the modern HTML5 web-based interface.
Launch the vSphere Web Client (Flash), select your vCenter, and go to Update Manager. Then go to Admin view > Manage > Settings > Host/Cluster settings > Edit.
Note: VMware supports Quick Boot with a limited set of hardware platforms and drivers but not on ESXi hosts that use TPM or passthrough devices.
Final words ^
Using Quick Boot on an ESXi host lets VMware VUM optimize the remediation time of hosts. If there are a patches or upgrade operations that do not affect the hardware of a host, Quick Boot is a real advantage.
When you enable the Quick Boot feature, Update Manager skips the hardware reboot (the BIOS or UEFI firmware reboot). As a result, the time an ESXi host spends in maintenance mode decreases, thus minimizing the risk of failures during remediation.
VMware Quick Boot significantly reduces the time needed for a host reboot, but there's only support for it on select platforms. At the time of this writing, only DellEMC and HP have hardware supporting Quick Boot.