Well, I've had my drobo for a while now. I really have no complaints on the hardware; it works as expected and works well. I do have issues, however.
My first issue is my own behavior. I sometimes fail to RTFM. In this case, it was the part of the manual on formatting. I simply formatted the drobo from Disk Utilities. If I had RTFM, I would have learned that the standard format was for 2 TB volumes – if you stick more available space in the system, you'd get multiple volumes. The drobo can be formatted to anticipate a volume of 16 TB, which would have made more sense to me. The drawback to this format is slower boot times, but I'm okay with that. In any case, it's simply a matter of reformatting the drobo and start over. Unfortunately, I have the older USB 2.0 drobo and offloading the data took at least a day (and some struggling to find the disk space). Now, the drobo is reformatted and I've started the process of moving all the data back! ugh! take my advice, if you get a drobo, RTFM.
The second issue I'm having is planning my capacity. Now, Data Robotics provides a nice tool to help you plan your space, called the Drobolator. My current drobo has 2 1 TB drives, 1 500 GB drive, and 1 320 GB drive. That gives me about 1.6 TB of usable disk space. However, I wanted to add space to the system so I started trying to figure out the most cost-effective approach. It's not so easy. In a pure cost-per-gig view, I should buy 1.5 TB seagates. However, if I bought only one, the cost per gig went up considerably because the drobo would only 1 TB of space, rather than 1.5 TB. This is because size of the largest drive has to be eliminated from the total capacity for data protection should it fail (e.g. if you have 3 1 TB and 1 1.5 TB and the system was full, you'd be protected even if the largest drive failed since the system would use only 3 TB of the 4.5 TB). Based on the fact a 1.5 won't get me anywhere, I went with a WD green 1 TB drive (cost $10 more than a similarly sized seagate, but supposedly uses less power). Now this set up leaves me with 1 500 gig drive. This drive, when it comes time to replace it, makes more sense to swap with a 1.5 TB+ drive. At this point, the costs go way up (depending on how long you wait). Any drive I swap into the drobo now must be the largest capacity of all the existing drives, not just equal to the largest. If I swapped the 500 gig for a 1 TB, I'd get an additional 500 gigs of capacity. If 3 total TB available is enough, that's not a problem. But what happens if I need another 500 gig later? If all 4 drives are 1 TB, I'd have to replace a minimum of two drives: the first would become the largest drive defining the space for protection, and the second would then provide the available new storage. Try that on the drobolator, 4 1 TB drives and swap one with a 1.5 or 2 TB drive. At current prices, then, to add 5oo GB to a drobo of 4 1 TB drives would cost about $260, a shift from 11 GB/$1.00 to 1.9 GB/$1.00. That doesn't include of the cost of pulling out the 2 1 TB drives.
I have to wonder whether at this point it's better just to buy a second drobo and use the working drives you pulled out of the old drobo when you upgraded. Maybe, maybe not. I do tend to use hard drives for backups that I keep in undisclosed locations. If they are full, then I don't have any drives available. Of course, I could use a drobo for that purpose instead of simple drives. I'll have to consider my options if and when my drobo starts running out of space again.