One evening we had a momentary power outage, causing sudden shutdown for my Mac mini and the attached Drobo (4 bay). When the system came back up, only one of the two volumes mounted on the desktop. The primary 2 TB volume is of course the one that didn't come up. But the Drobo shows no errors or problems with the unit.

Disk First Aid, er... I mean Disk Utility can see that there's supposed to be a volume there (HFS+/Journaled) but cannot mount it. Using the Repair function leaves me with two error messages after 3 hours: "Incorrect Number of Thread Records" and "Invalid Node Structure". Running fsck_hfs -ypr on the drive gives the same message as Disk Utility.

Disk Warrior wouldn't touch the volumes, but Data Rescue 3 trial version can see it and has also recovered a file from it.

Can I safely recover the files from the first volume into the second volume on the same Drobo?

1 Answer 1


Drobo Support told me to NOT recover from one unmounted volume to another, but did not clarify why. It seems odd that there would be a potential of overwriting the first damaged volume, so I don't understand what's going on here.

Fortunately I was able to find an external hard drive that I could recover the most critical files to using Data Rescue 3. (New purchase for $100).

Moral of the story: Buy a UPS for your Drobo. That may have prevented this problem.

  • I also learned the hard way to UPS the first-gen, 4-bay Drobos. In fairness: most RAID solutions have this problem. If you interrupt them before a cache flush you risk corrupted volumes. It's a speed/fragility trade off.
    – Ian C.
    Feb 24, 2012 at 20:05

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