I’ve had this Drobo since 2009 working well with 4x 16TB drives & Firmware version 1.4.2 [1.254.50341]
I can buy 2+TB drives and replace as I go like normal, but I wanted to re-purpose my old 1TB drives sitting in their cardboard boxes; i.e. keep what is on the 4x1.5’s and create a new “swap in/swap out” volume that I can place my iTunes movie library on.
I stopped my Drobo, took out all 4 1.5TB drives, put in 1x1.5 and 2x1TB drives and booted it up.
All 4 bays are showing Red and I see a message in the Drobo Console stating that I’ve removed too many drives all at once and to do them one at a time.
So based on the error, I can only guess the Drobo thinks the 4x1.5TB drive set should still be in the bays which leads me to believe it can only deal with one set of drives ever that grows. True?
All I wanted to do was format them as a new volume, put some data on them, remove and replace them with the older volume I constantly use.
What you want to do is possible - have two or more swappable sets of drives.
If you are having trouble formatting the entire set, for the time it takes, remove two of the drives and format the two remaining drives, using the Dashboard, into the partition schema you want. Once completed, add in the additional drives. The drobo should see the new drives and asked what to do with them.
Once the drives are configured, use some method to mark the drives to identify the set name and the bay the drive resides in - the second part is important. I use green painter’s tape.
You should now be able to swap the drive sets as needed.