According to the RAID card management interface the RAID1 is completely fine and running as optimal. I see if I can run a verification but to be fair the times something went wrong at hardware level it never failed to warn me...
In the meantime I've tried an "upgrade" over the same ESXi version, as expected it completes fine but for some very strange reason it spends a good 5 min on "activating jumpstart plugins" but eventually it progresses.
Then after completing and rebooting it gets stuck on a loop (blanck screen + quickly the error message here below):
Hum... this seems to be bigger than expected 😕
Ok so here goes the story.
For this type of issue "upgrade" will not resolve anything.
I got some luck selecting installation without formatting VMFS volume.
Needed to reinstall licenses, reimport VMs etc.... still less time that t took me to try to resolve the issue as per OP.