Drobo overestimates used space

Here’s what happens. When the Drobo is connected to a computer and the Drobo Dashboard software isn’t running, the Drobo’s capacity meter will overestimate the used space, potentially triggering a low space alert. When the Drobo Dashboard software is started, it does its own used space calculations and corrects the capacity meter, literally turning off one to two or even three of the blue LEDs that indicate how much space is used.

There are 10 blue LEDs, one for each 10% of space used on the Drobo. When I connect one of my Drobos to my computer, the capacity meter lights up 9 of the LEDs, indicating 90% disk space used. When I start up the Drobo Dashboard software, two of the lights are turned off, leaving 7 on, or 70% disk space used. Also, although low space warnings are triggered when the Drobo Dashboard is started, after it calculates the space used, the warning go away, and the Dashboard screen goes from yellow to green.

I made a video which shows this quite clearly. I apologize for its poor quality, but I made it without any prior setup, just to show you that I’m not making this up. This also happens for my other Drobo, where the capacity meter shows 50% disk space used when I connect it, but drops to 30% disk space used when I start up the Drobo Dashboard. If you have a Drobo yourself, try it out and see.

Download Drobo overestimates used space (640×480, MP4, 35MB)

I notified Drobo Support of this issue a couple of days ago, but I have not yet received a reply from them. I will be glad to include any feedback/clarification from them right here, and will update this post with further information as I receive it.

I should also point out that there’s still no fix for the other two issues I outlined in my original Drobo review recently, where I pointed out that:

  • The transfer speed slows down significantly (and somewhat inversely proportional) to the amount of disk space remaining on the Drobo after the 70% mark is reached. In other words, the less space there is (in terms of the percentage, not GB remaining), the slower it’s going to be to access and transfer data to the Drobo.
  • The Drobo becomes excessively noisy when the fourth hard drive is inserted, and the fan will go into high gear when the Drobo isn’t even used. It seems this is loosely tied to the ambient room temperature, and once it goes over 75 degrees Fahrenheit, the fan kicks on and stays on for a long time. But again, you’ll only see this issue when the 4th hard drive is inserted. Given that the Drobo is a consumer device which is meant to operate at room temperatures, not in a climate-controlled server room, this is not appropriate behavior and should be corrected.

3 thoughts on “Drobo overestimates used space

  1. Exactly the same happens with my Drobo Pro. I notified Drobo support and they suggested a larger disk replacement. It seemed like they did not understand that the problem was only at startup, waiting for Dashboard to accompish its launch and connection to Drobo, while the physical disc capacity was OK.


    1. If they didn’t understand, keep insisting and explaining until they do. It’s really just a matter of a firmware fix, so the upper-level engineers, the one that are working on the firmware, need to know about this issue.


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