Switching off your NAS/DAS devices for the holiday is a proven way to kill hard drives (that won’t spin up again).
In this case one of my oldest¹ failed and I had to replace it right away.
My Drobo started rebuilding the data on the new disk and, a little after two days, I have a fully working DAS again 🙂
This happened two or three times in the last five years without any problems. I really trust my Drobos and I’m considering buying another one (a faster one :).

1. a Western Digital Green WD20EARS [↩]