I know, they're different animals. But here's my dilemma. 27" iMac with 3tb fusion drive. I don't have 3tbs of data yet but would like to get a setup for time machine that doesn't require me to make wholesale changes later. If going with the 5D I would start with a couple of 3tb drives. Leaving ample room for growth as i approach the 3tb limit on the iMac. Understanding the time machine requires more than 3tb to backup 3tb. Cost is probably a little over 1k, I think. A concern with the Drobo is restoring. I'd like to setup the new device as the time machine target on the MacBook Pro I'll be replacing, back it up and then attach to the brand new iMac for initial setup. Both of these steps would be using USB I guess. Can I then switch to thunderbolt on the new iMac? And if I have a failure and have to restore the system from the Drobo can I do that using thunderbolt? Wouldn't it be an issue that the newly restored system wouldn't have the Drobo thunderbolt drivers installed yet? Other option is the J4. This would be my choice over the Drobo mini because of cost mainly. The problem here is that I can only get the J4 with a max of 4tb because of the 2.5" drives (there may be larger drives, not entirely sure). If 2tb drives do exist later I'd have to swat out all four. And if the larger drives are only 1.5tb them the total of 3 in Raid1 wouldn't allow time machine to back up the whole HD. I want a solution that lets me reliably back up the complete 3tb HD with time capsule and have redundancy. Cost of roughly 1k or less is the budget.