... and one more failed drive in my Drobo. A WD Green, 4TB.
This is starting to get a bit unreal. I am checking the failed drives SMART status tomorrow in the office.

I am now thinking the Drobo is killing them (I would assume poor coolingt). So far the ones I checked were in face dead, so it seems Drobo is correct in that.

I am now keeping my Drobo without the front cover, in the hope cooling improves, IF that is the issue.