Which hard drive to replace?

In my 4-bay drobo the top drive is suddenly constant red. The dashboard says my Drobo is critically low on capacity and that I should replace the hard drive indicated by the red light with a larger hard drive.

This puzzles me. I have this setup:

4 TB
4 TB
3 TB
3 TB

Why does it ask to replace one of the 4 TB drives and not one of the smaller 3 TB drives?

Does this make sense? Could it be that the dashboard is wrong? And what would happen if I takeout one of the “green” 3 TB hard drives and replace it with a 4 TB harddrive? Wouldn’t that make more sense?

Kind regards,


hi peter,
as far as i know the drobo will usually indicate to remove a smaller drive (usually the 1st/topmost smaller drive if multiples exist), but there may be some cases where it will suggest a different drive, for different reasons…

for example, maybe the top drive in your case, is detected as having several ‘softer’ issues with it…
if you can have a look in dashboard, can you click on any drive (or using drop down menus) can you see any more info about each drive, in case any are showing labels such as Warning or Healed?