I must admit to not knowing about this until I stumbled upon it vSphere 6.7 has added a new feature called QuickBoot.

Quick Boot enables the ESXi host to restart straight into the ESXi load screen avoiding the initial POST and memory test screens. This is particularly cool when you are doing ESXi updates as the reboot time is dramatically shortened as shown below.

So how does it work?

• When a reboot is necessary, devices are shut down and the hypervisor restarts
• Hardware initialization and memory tests are not performed
• Improves host availability and shortens maintenance windows

​Requirements

• Supported server hardware (current: shortlist of Dell and HPE systems)
• Native device drivers only – no vmklinux driver support
• Secure boot not supported

How to enable it?

​Quick Boot is primarily intended to benefit Update Manager workflows, there are stringent checks for compatibility, according to the following files

• /usr/lib/vmware/loadesx/whitelist.txt & platforms.txt

​It is also possible to enable Quick Boot from the ESXi console

• /usr/lib/vmware/loadesx/bin/loadESXCheckCompat.py
• loadESXEnable –e

​To test whether or not the last reboot was quick or normal

• vsish -e get /system/loadESX/isBootLoadESX

Additional troubleshooting info can be found in the logs

• /var/log/loadESX.log