UCS C220 M6S VMWARE 8.0.1 legacy boot detected

[AdamG73545]

After upgrading 7.0.1 to 8.0.1 I see this message: BIOS_FIRMWARE_TYPE_WARNING: legacy boot detected ..... 

Not sure if I can ignore it or if should I change BOOT to UEFI? 

[Steven Tardy]

Changing from Legacy BIOS to UEFI (while it may function) isn't supported by VMware (according to a prior VMware support case).

So if you do change from Legacy BIOS to UEFI, then I would suggest reinstalling ESXi (make sure you have your keys/licenses saved first).

[riaan.vanniekerk]

As per VMware KB article Deprecation of legacy BIOS support in vSphere 

• vSphere 8.0 will drop support for legacy BIOS for new server platforms (Intel Cascade Lake and onwards; AMD Rome and onwards). This will apply to all new server platforms, regardless of the server CPU series.
• In a future version of vSphere, VMware will completely deprecate and remove support for legacy BIOS, and hence strongly recommends that customers start evaluating the UEFI boot mode as default in their environment.

According to this article and many users on Reddit, switching from legacy to UEFI boot mode does not require a reinstall. We are planning on switching from legacy to UEFI on ESXi 7.0 before upgrading to ESX 8.0. So far my testing in a lab, on a handful of M4 (which do not support ESXi 8.0) and M5, we did not have to reinstall any hosts. We are only focusing on switching to UEFI, not turning on Secure Boot.