Excellent scalable storage system that saves the environment

I have bought this unit as a stopgap measure between an external 4TB HDD and a full-blown RAID system such as LaCie 6big or 12big. By inserting the 4TB HDD and a few older 2TB HDDs into the Drobo, I got enough capacity for the foreseeable future. (The 2TB HDDs would otherwise have to be recycled, even though they still function.) The unit is very quiet -- I can hear the fan only when I put my ear right next to the fan. The best feature of all Drobos is the ability to use any 3.5" SATA HDD, as opposed to conventional RAID systems that require HDDs to be of the same size and model. When you need more storage capacity, you just replace the lowest-capacity HDD with a larger-capacity HDD.
The only gripe I have is the external power supply: I would have preferred it to be internal... but then the Drobo fan would have to run at higher revs and make more noise. Ergo 5 stars.