The server is old and requires some hardware maintenance. Database server SSDs are failing often so switching them out.
Who knows really. It should take only few hours.
UTC 0800: Site offline
UTC 0945: Data transfers are a bit slow from backup... Two hour estimate.
UTC 1140: Taking a bit longer than expected. Two hours was for first part only. Next takes 10h or so... so site will be down for a while.
UTC 2230: Still chugging along.