Hello, Mark Fuccio from Drobo here.
Some comments. First, there are several model Drobos, and they have *very* different performance characteristics.
The 4-drive Drobo has FW800 and USB connections. Good fit for bulk storage or backup. Not recommended for editing HD.
DroboPro is an 8 drive system that uses iSCSI/Gigagit ethernet. Its fast. Perfect for editing. Using Blackmagic’s Disk Speed test rates it 90MB/sec read, 80MB/sec for writes. iSCSI support requires OS X 10.5.6 or later. I wonder if Rob, the poster above, might have used an unsupported version of OS X.
DroboElite is an 8 drive system with twu iSCSI/Gigabit ethernet ports. Rich Harrington, who has a large presence here, uses one in his studios at RHEDPixel and has 3 editors doing multicam work on it almost every day.