Hello there. I have a Drobo 5N (Firmware v3.1.1) with 5 x 2 TB drives. The details are as follows:
Bay 0: 2 TB, WD Red with NAS Aware 2.0 (WD20EFRX-68Exxxx)
Bay 1: 2 TB, WD Green (WD20EARS-00Mxxxx)
Bay 2: 2 TB, WD Green (WD20EARS-00Mxxxx)
Bay 3: 2 TB, WD Red with NAS Aware 2.0 (WD20EFRX-68Exxxx)
Bay 4: 2 TB, WD Red with NAS Aware 1.0 (WD20EFRX-68Axxxx)
Note: Drobo Dashboard does not display the last 4 characters of the Product ID.
I recently bought 2 new 4 TB, WD Red drives. Both have NAS Aware 3.0, manufactured on Nov 12 2014, model “WD40EFRX-68WT0N0”. I got these to increase my Drobo 5N capacity further and to replace the old WD Green drives. After confirming that my Drobo 5N was healthy, I proceeded to remove the drive on Bay 1. LED changed to SOLID RED on Bay 1, and the other 4 drive bays quickly changed to “Data protection is in progress” mode and the LED changed to FLASHING YELLOW/GREEN. I proceeded to insert one of the new 4 TB drives on Bay 1. Nothing happened. No drive spin up could be heard or felt. LED remained SOLID RED. All the other drive bays stayed intact, as in “Data protection is in progress” mode. I re-inserted the same drive once again, but nothing happened. I proceeded to insert the other new 4 TB drive, and nothing happened as well. I proceeded to test the drives on an external enclosure and hook them up to my PC and they loaded, spin up just fine.
In summary, the drives were fine on an external hdd enclosure but, the Drobo 5N did not powered either of them up. So I made one final thing.
I proceeded to re-insert the old 2 TB drive I removed from Bay 1, and it spinned up and joined all other drive bays in “Data protection is in progress” mode right away.
I have no clue about why these new 4 TB drives are not working with the Drobo 5N, but I am sure something changed or something needs to be updated on the Drobo 5N firmware to recognize these drives.