5D Displays Bay Critical Despite having ample free space

I have a 5D which had 5 x 10TB Drives in it.
I am migrating all of my data across to a Drobo 8D using Carbon Copy Cloner.
Once a large portion is completed copying, I delete the original content off the 5D, which creates space.

Once I had enough overhead, I removed one of the 10TB drives from the 5D and put it in the 8D.
The 5D went into data recovery mode, and eventually showed the now empty bay as critical, indicating I needed to put a drive in.

I put a 4TB drive in, and after data recovery mode, the bay still shows as critical.
I tried removing the 4TB again, hoping it would prompt some sort of re-calibration, but with the bay now empty, it still shows it as critical.

The unit has 40TB of Drives in it, for an effective usable total of 27.13TB and only 12.31TB of that is in use.

From what I understand, I should be seeing all green lights as there is enough available space in single disk redundancy mode?

I have tried Shutdowns, re-starts, removing and re-installing the disk packs, booting the drive with no disks etc.

Any info would be much appreciated!!!
Mac OS 10.15.4
Drobo Dashboard 3.5.0
5D firmware 4.1.3

As far as I can tell, you have performed all the correct procedures, however there is not an option on the Drobo to force a re-allocation of data across 4 instead of 5 disks! Some posters have successfully downgraded their HDDs in size but I have yet to come across one who has reduced the number of HDDs - until you.

First comment. Make an external backup of your data.

Option could be then to reformat the drive completely first with 2x10TB and progressively rebuild it by adding your additional 2 10TB (1 at a time until green), then reintroduce your data into the new arrangement. You would obviously need to reset any file links that get broken.

Thanks for taking the time to comment.
Yep… a Format / reset back to factory is exactly what I think is needed to correct the issue.
The problem is, I need the 10TB drives from the 5D to make enough room on the 8D to be able to safely migrate the data across before I can format / reset!
I may have to go buy a few additional drives, even if I end up with extra in the end.

Again, appreciate the help.


In an interesting twist somehow, the Drobo managed to sort it self out, and the critical warning disappeared.
Whilst that is great… I can’t replicate the fix, and now have another drive that I downsized with the same issue.