Issue The host goes into an un-responsive state due to: R20;Bootbank cannot be found at path ‘/bootbank” and boot device is in an APD state.
This issue is seen due to the boot device failing to respond & enter APD state (All paths down). Some cases, Host goes to non-responsive state & shows disconnected from vCenter.
As of 7.0 Update 1, the format of the ESX-OSData boot data partition has been changed. Instead of using FAT it is using a new format called VMFS-L. This new format allows much more and faster I/O to the partition. The level of read and write traffic is overwhelming and corrupting many less capable SD cards.
The action plan for future resolution would be to replace the SD card/s with a capable device/disk. Per the best practices mentioned on Installation guide.
The version 7.0 Update 2 VMware ESXi Installation and Setup Guide, page 19, specifically says R20;As even read-only workloads can cause problems on low-end flash devices, you should install ESXi only on high-endurance flash mediaR20;.
https://docs.vmware.com/en/VMware-vSphere/7.0/vsphere-esxi-702-installation-setup-guide.pdf
You can also refer to the below KB:
Reference: https://kb.vmware.com/s/article/83376?lang=en_US
Resolution
VMware engineering has a fix that will be in the next release. Planned for July 2021.
https://communities.vmware.com/t5/ESXi-Discussions/SD-Boot-issue-Solution-in-7-x/m-p/2852027
https://www.provirtualzone.com/vsphere-7-update-2-loses-connection-with-sd-cards-workaround/