I would not recommend a Drobo (2nd gen). I have had nothing but problems since buying one this April, and then another to address issues caused by the first one.
The problem is that the Drobo randomly unmounts, and this has the potential to cause huge data corruption issues. There are many agonizing wails on the web from other Drobo owners stewing in a similar soup. Support on this issue -- to the extent that you can quickly and easily recover your data -- is almost non-existent, and Drobo has not released any firmware that stops this from happening.
To be fair, the newer models seems to be getting more updates, and perhaps they are better, but I am now moving to a more robust solution (pro RAID NAS solutions from Netgear or Qnap). Aside from the reliability factor, the speed boost alone can be worth the price of admission. Yes, they are expensive -- but the cost pales in comparison to the effort required to try and recover 4 to 8 TB of data.
In the end, everything is easily replaceable as long as you have the funds. But data loss in a increasing paperless world can be harrowing experience.
Oh yes, in case you do use a Drobo, then avoid the Seagate LP drives (the WD Green drives are much more reliable in these devices).
Hope that helps,