Well a Drobo is a device you put drives INTO. If that failed and took the drives with you (unlikely but not imposable) Then your other setup would have 1/2 your data. That's my only point.

Drobo is about data loss due to a drive failure. ALWAYS have a backup of your most important files somewhere else for true data backup redundancy. (and keep one set off site for disaster recovery if your files are super important)

Basic backup rules.

Roman