I waited until the computer was done using the Drobo and via the dashboard I told it to restart.
When it came back it only reported a fraction of the storage and most to the empty drive space went to “overhead”.
On the dashboard the Drobo system has a yellow light but all the drives are green and the data is still there.
Running firmware 3.1.1.
MacOS 10.9.5 on one machine and MacOS 10.8.5 on another.
So what does the yellow light mean?