I just want to take this opportunity to warn people off buying a Drobo and/or DroboShare. For those who haven't heard of it, Drobo is an impressive-sounding box that you slide drives in and out of as you like, and it manages all the RAID and defragging and whatnot.
The acute problem is that without warning they can screw themselves up and refuse to mount. When this happens you are completely hosed because nothing except a Drobo can read the Drobo disk format. You will need to format and restore from backup. What's that, you say? You bought the Drobo because it seemed like the safest way to keep 8TB of storage going, given that that's really hard to back up? Tough tits. Yes, I know "RAID is not a backup" etc, and I did have actual backups from which I restored my data, but the difference between the Drobo marketing and the Drobo reality is staggering, especially given the Drobo cost.
The chronic problems? Drobo is slow, glacially slow. For some reason the makers claim that it can be used as "primary" or working storage, which is a laugh since the access times are significantly slower than a plain USB2 drive which is already uncomfortably slow for serious work. It will drive you nuts. The management interface will drive you nuts. The way Drobo lies to the OS about its capacity and available space, so you have to use the management interface to find out this basic information, will drive you nuts. And you will live in fear that unmounting the device by any means other than the management software will corrupt your data unrecoverably. Gods forbid you knock the USB cable out by accident.
DroboShare is the additional expensive component that turns Drobo from a USB drive into a NAS. It has its own problems. The least of which are that once you switch to DroboShare, neither Time Machine nor Lightroom will let you use the Drobo storage.
I thought Drobo was a great idea, it sounded awesome when described, I think CK even had good things to say about it, but I was wrong. It was a very expensive disappointment. This is my story.
tl;dr: Drobo and DroboShare suck, do not buy. Or if you must, buy my one.
All of http://www.devwebsphere.com/personal/drobo/ is a tragicomedy really, he bought one in 2009 and quite liked it for the first week, then spent 24 months battling with every problem I described and more, and he still hasn't given up! Me, I nearly stroked out when Disk Utility said "won't mount, can't fix, it's dead", and I never trusted it again after that.