I currently have 3 500 gig drives in my drobo and am at 60% usage. I have noticed that the fans run a lot more than they used to. I presume that is due to percentage of usage? I am also going to be buying a 1 tb drive to put in the fourth bay. That way as I run out of space I will just start pulling the 500 gig drives and replacing them with 1 tb drives. Question, how would I erase the data on the 500 when I remove them from the drobo?