Mix Red and Green Drives

I am going to undergo the task of rebuilding my Gen 2 Drobo. I’ve been having a few issues with my Drobo and after running Disk Utility and Disk Warrior, they both recommended that I backup my data and reformat the drive (Drobo).

I have to purchase a new drive to back the data up to and was thinking about going to a WD Red drive. I currently have WD Green’s in the Drobo. My plan was after rebuilding the Drobo replace one of the smaller drives with the Red and then purchase Red’s in the future.

My question to whomever is, is this a good idea? Will there be any performance issues or compatibility issues? I can’t imagine anything being slower than the Greens currently in it. The Drobo primarily serves as a TimeMachine repository and iTunes server.