When you initialized your Drobo you must have told it to "pretend' that it has 16TB which is the Max default setting I believe. That's how the Drobo works so that it can expand the storage space without causing your computer to reformat it when you add additional or larger capacity drives. The Drobo lights will tell you when it's getting full. Also the Drobo dashboard utility will tell you how much is actually being used.

I have my Drobo formatted to 16TB as well and I only have 2 1.5TB drives in it. However, I don't have it connected to my Pogoplug. Each light on the bottom of the Drobo indicates 10% utilization of the current capacity installed in the Drobo.

If the Drobo didn't work that way then you'd have to reformat the entire Drobo losing all of your files each time you added capacity. The limitation is not with Drobo but with the computer OS which typically can't adapt to a drive changing sizes on the fly.

One word of warning though is Don't let the Drobo fill up because it will likely then corrupt your drives and you could lose everything stored on it. Pay attention to those lights and when it "asks" for additional storage then feed it another drive.

-Mike

My Drobo predates my Pogoplug by about nearly a year and I didn't want to repurpose it on the Pogoplug. I also already had an external 500 GB USB disk not being utilized so it was available for use with the Pogoplug.

I use Drobo for my TimeMachine backups. Using the Drobo with the Pogoplug helps to keep your Pogoplug files safe but the Pogoplug could never take advantage of the potential speed the Drobo could bring to bear. Of course me using my Drobo for TimeMachine backups is also a waste as far as speed goes. I use it because I want to be able to depend on my backups.

It's risky to use the Drobo as I am though because with an automated backup like TimeMachine it could potentially exceed the currently installed disk space and cause the Mac to corrupt the drives in the Drobo because after all the Mac thinks there's 16TB of space. So I have to keep a watch on those Drobo lights.

The smarter way to use the Drobo would have been for me to create a partition on the Drobo for TimeMachine backups that was equal to or less than the installed capacity -- then use any remaining or added capacity for things other than TimeMachine backups.

I think there are Drobo Apps out there now to help with TimeMachine considerations but the Drobo is working as advertised and I just have to do my part and monitor the current usage frequently enough so that I don't get bit.

I wanted to have a TimeMachine backup disk that could grow with advancing drive capacities so I wouldn't get into the problem of buying a new Mac that came with a larger capacity drive than an existing (non-Drobo) disk that I might have been using with the old Mac. That way I could easily move the TimeMachine disk (Drobo) to a new Mac and it would still have all of my old files plus plenty of potential capacity for the future.

Since TimeMachine became available iMac boot drives have grown from 500GB to 1TB to 1.5TB to 2TB. A 500GB backup disk for a 2TB internal won't work very well as you know. ;) And yes, my first TimeMachine disk was a cheap 500GB USB drive. That's actually the one I moved to the Pogoplug.

I decided that I'd let TimeMachine do what it does best which is backup to a directly attached disk and let the Pogoplug Drive utility do one of the things it does best and let it copy designated folders that are safe on my Mac to the Pogoplug for availability on the Internet. That way if I lose a Pogoplug drive then I'm not losing anything copied from the Mac but only files directly uploaded to the Pogoplug which is still a concern just not as big as losing everything would be.

The best solution I think would be to have a Drobo both places. Maybe someday... I can dream can't I?

-Mike