Drobo Gen 2 won't mount to Mac....

I have a Drobo Gen 2 with 4 WD 1TB drives inserted.

I’ve been using it attached to my Netgear Router via USB.

A couple of days ago, it disappeared.

I connected it directly to my Macbook Pro running 10.11.5 (El Capitan).

The Drobo Dashboard sees the box, but when I click on it, a pop up notifier says there is a new volume that needs to be formatted. I have not inserted or removed any drives. There’s no reason for a drive to need formatting. The Dashboard also says that I am using 1.85TB, I have 2.71TB free of a total 2.71TB. Huh? That math doesn’t add up.

In Disk Utility, Drobo shows up in the sidebar but it is greyed out. When I click First Aid, it fails and says: Invalid Node Structure. Operation Failed.

I’m spent a few hours reading over various posts on the Internet, but haven’t made any progress.

I also connected the Drobo to my wife’s Mac running OSX 10.9.5, but it has the same issues. I’ve tried multiple USB cables and ports.

The lights next to the drives on the Drobo are green, the power light is green, and the 7 of the 10 blue lights are light. When I restart the Drobo, it goes through a normal boot sequence.

I think I’m at the point where my only option is to purchase Disk Warrior. There’s vital info on the Drobo that I need to recover.

Any suggestions are appreciated.

hi tmaranda,
can i check how long you have been able to successfully use your drobo when connected to the usb router in the way you mention?
and also if your drobo has always had 4 (x1TB) drives inside it when you set it up?

can you also remember how large the volume (or drive letter) was showing you as its max size when it was working?


I have used it for over a year while it was hooked up to the USB port on the router. It’s always had the same drives since I started using it.

I don’t recall the max size it was before it failed.

I ended up purchasing DiskWarrior and it identified a huge list of errors. It was able to repair enough to allow the Drobo to mount.

Even with that, there a still a huge swath of files that are missing or corrupted and inaccessible. The most painful of which is 1000’s of photos, mostly of my kids, spanning the past 8 years. I’m not writing those off as totally lost, but this whole experience has been disturbing.

thanks for the info tmaranda,
(ouch that you were only able to get some of the files…)

can i check if you ran diskwarrior (via the router?)
if not, you might be able to try diskwarrior again, when directly attached to the computer (though please only try this 2nd pass of diskwarrior after you have made a backup of your current data just to minimise any further issues)

also, while i do not have a mac or diskwarrior, it might be worth doublechecking some more manuals or guides of diskwarrior before any more passes, just in case it actually made copies or moved the inaccessible files into another location that you could try accessing. (for example some programs make a lost and found folder, or on windows some tools used to generate a bunch of partial files which actually were the original file just moved or renamed with a chk extension)