The two 3T hard drives arrived today. I installed them in seconds. While it was running, I took the faceplate off the Drobo, and inserted the first hard disk. There was a short pause, like 5 seconds, then the green light beside it went on, and a notification popped up on the Mac Mini to tell me that a new drive had been inserted in the Drobo. I did the same with the second hard disk, same thing happened. So now I have two 500G drives and two 3T drives in the Drobo. This is what the Drobo Dashboard now shows:
It confirms and shows the capacity drives that have been inserted. I looked at how the drives are being used, and the Dashboard shows this:
That explains a lot.
The default is to be able to handle one drive failure. There is a setting to allow two hard drive failures, and I investigated that. Instead of giving me 3.5 T of usable data, it told me I would be down to 950G of usable data. I did not change that setting.
And finally, I wanted to see what my current usage was, and the Dashboard showed me this:
I'm pretty happy with it so far. But I'll be happier when those two 500G drives are replaced with two more 3T drives. I'll do that next month.