hi dangerfrog, are you using windows?
when i ran dashboard service on an old xp machine in the past, i sometimes had to shut it down as it was taking up about 5-10% cpu… (often after i rebooted the machine, it was ok again though)
maybe you could try that too as a test (shutting down dashboard, and rebooting too)
for your space issue, if it is your gen3 that you upgraded a 4TB into a 6TB, is the 2nd drive showing you a solid red light?
(can i check is your 2nd drive also a 3TB drive as well? - if so, it might just be that your drobo was getting a bit low on overall space, but since the size of your largest drive is used for protection, it might just be that once you upgrade your 2nd drive, it will actually be able to use the extra space that your 1st drive now has been upgraded with)
if you post back when you get a moment with full details of the drives sizes that you have in your drobo we can go through a breakdown of the sizings together if you want