Have you ever asked yourself what happens when the USB device / SD card where you have installed ESXi fails?
The good news is: nothing (in the short run)
ESXi is loaded into memory while booting – so there is no impact on ESXi when the device fails.
All virtual machines will continue to run as usual, all services/features you know and love (eg. vMotion,…) are still available, too.
Another piece of good news is that this case is monitored by ESXi and you will receive a notification in your vCenter:
“Lost connectivity to the device … backing the boot filesystem. As a result, host configuration changes will not be saved to persistent storage.”
Of course, if you try to reboot the ESXi host now, the reboot would fail as the host has no working boot device!
What you can do, is to put the ESXi host in maintenance mode and shut it down. Replace the broken SD card/USB device and install/configure the ESXi host new.
By the way, a hardware monitoring tool like HP SIM can also report faulty internal SD cards. You will get errors like “Embedded Flash/SD-CARD: failed restart“