Drobo redundancy

Question

Given the inexplicable demise of Drive Extender technology in Windows Home Server, I am considering other options, such as replacing it with Drobo (and a linux server).

One thing I'm not 100% clear on is the unit of redundancy in a Drobo. In WHS, I can set a specific folder as requiring redundancy and let other folders "live on the edge" without any redundancy. From what I can tell, it sounds as though with Drobo it's an all or nothing affair. I can specify that I want to be able to recover from a single HDD failure (or maybe even two) but I can't say "don't worry about creating redundant copies of these files".

Am I right in my understanding?

Answer 1

Yes you are right. Effectively, the capacity of the largest disk in the Drobo is lost for redundancy. During regular use, you can think of it as a RAID 5 system with some flexibility regarding extensibility and drive sizes.

Screenshot of my Drobo Dashboard:

The overhead is negligible, and used for protection (1.83 Tebibytes) is exactly the size of one of the largest HDDs (2 Terabytes).

(Note that the "maximum capacity" of the volumes is only a virtual value I configured -- I don't know what happens when the Drobo fills up but the volumes tell my system there's space left for use)