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What I can say about the Drobo 5c is that for most people this is overkill. It is a fantastic backup plan and you would never need to worry about any drive failure depending on how many drives you have installed in it. One drive fails and you just pull it and replace it. There are many makers of Raid drives. All are good. Just depends on what you are using it for.
I use Pegasus, G-Technology and Seagate for my backup and storage. But I have TB's of video & graphics that I use for design. I also use mine for movie storage as I have over 1100 DVD's I have converted for use with iTunes.
As I said, for the average user the Drobo will be overkill. If your planning on using it for backup only, then there are better & cheaper alternatives.