i think up to 10 days would be all that is needed for a (normal rebuild) after upgrading your drives.
eg, i had about 5tb of (raw drive capacity) and it took between 4-5 days for me to upgrade my gen1 (and that was just from 4x1tb into 2x1.5tb and 2x1tb).
If you have been waiting so far, might as well give it a bit more time…
What “could” be happening is something like these:
upgrade is taking more time because your drobo is still connected to the computer, and something else might be slowing it down by using it in some way.
(you could try disconnecting the cable from the computer)
upgrade is taking more time, because another drive of yours maybe encountered some stress-problems and it had to do some more rebuilding.
upgrade is taking more time, because maybe there are some hard drive errors on the drives and drobo is having to work around it and it takes more time. (a diagnostics log could show if a particular drive is failing, but i wouldnt run the diagnostics just yet as it might interfere with the rebuild)
What i would do if it was me, would be to give it a couple more days,
and then shutdown the mac and disconnect the fireware cable. (so that the drobo is just with the power plug)
and then listen to the drobo/touch/feel vibrations etc to see if its “doing stuff”, and then leave it for a few days on its own with no computer attached.
(if you feel that after that you have waited too long, you could try to power down the drobo, wait 5 mins, and then power it up again, and then let it boot up again and see if it starts continuing again/rebuilding.)
if you dont want to power off the drobo, and have waited for a lot of time, then you could try rebooting the mac and then plug the drobo cable back into it to see in case it was the mac which needed a reboot as well.
(i’ve had a few “scary moments” with my gen1 and gen2, especially after a power cut, and it took a few restarts and an overnight rebuild/letting it run on its own, and then all was ok).
hope it helps a bit[hr]
also, as toby said, there might be some limitations with your particular dashboard or firmwares, but you need to make sure before doing that, in case its half way rebuilding with 1 version and then gets stuck trying to finish off with another firmware etc.
my gen1/gen2 units run fine on dash and firmware 1.3.7 and 1.7.3 (or vice versa) but i havent tried upgrading any drives beyond 1.5tb yet.