Empty Drive Bay LED is orange, Mac locks up

I’ve been having problems with my 5D lately. The Mac would stop functioning displaying either a spinning-pizza-of-death or completely locking up. I would have to force it to turn off in order to restart. Then I started noticing that the empty bay on my 5D would go from blank to orange/yellow LED display when this happened to the Mac.

I reinstalled my Mavericks operating system from the Recovery volume. I tried running Disk Utility and Disk Warrior on the Drobo and internal drive and sometimes it would lock up running those as would Drobo Dashboard. It would even prevent orderly shutdown of the Drobo. Still no relief from this problem.

Finally I read something about a procedure to (1) power down the computer and the Drobo, (2) eject all the drives from the Drobo, (3) start up the computer and Drobo Dashboard, (4) then start the empty Drobo and shut it down via Drobo Dashboard. Then (5) reinsert drives and start it up, and let it “rebuild” for a while. It’s been 15 minutes now and the problem has not returned yet.

Does anyone know why the empty drive bay light would be lit, what it means or what causes this? I couldn’t find any support articles describing this, nor forum messages.