After upgrading to Mavericks your Drobo might not show up in Finder (here it did just fine, using a Drobo FS800 (aka 2nd gen Drobo) connected over Firewire). If that happens, do either one of these to get your Drobo visible in Finder again:
- Unmount the Drobo from Disk Utility (where it by magic will appear!?) and mount it again by reconnecting it to your Mac.
- Unplug and put back the power to your Drobo, after which it will restart.
One of those should do the trick in case your Drobo might be missing.