>>42659456
HDDs are a bothersome bunch considering that they go to bed whenever there's no activity (which is good for their health if they're not a CCTV drives!). I personally don't do anything about it, but if you must insist on 24/7 activity you're going to have to make some script that writes or reads from the drive every minute or so, so it stays up all the time.
I don't know how hibernation might actually affect the performance, but I believe that it might spin up the drive faster since the data on it is already somewhat cached as opposed to a full system reboot. I might be wrong on that however.
Good luck.