Sorry, but that is incorrect; I currently use not one, but two 1TB USB drives (using a hub) with my Airport Extreme to back up an iMac, two MBs, and one MBP using TimeMachine. Works like a charm!
I think the Drobo would be overkill for this purpose; I have a 4TB unit that is used for media storage. As far as I can tell, you could hook up a fair number of USB drives to the Airport Extreme for a lot less $$ than a Drobo...
o/ Let me introduce myself, I'm known as overkill.
I have a Mac Pro, iMac, and a Macbook in my house. Between the three I have just over 2.0TB of storage, wit about 1.2TB in use so far. This is mostly RAW files from almost eight years of family photography, a bit of digital home video, and more music / TV shows than I want to count worth of iTunes Music Store.
I've been using a Time Capsule since it came out, but as I feared I've filled the thing. In my efforts to research an external drive to put on the thing I've tried a few different products.
Product #1. The HP MediaSmart EX485. hate the thing. I don't know why this won best of show because the Time Machine support sucks. You can only back up to the size of the hard disks, even if it supports four of them. It's not mentioned on their site anywhere but if you try and save money and buy say 750GB drives instead of 1TB or 2TB drives and put four in for 1.5TB of space you get a surprise that your biggest Time Machine backup is only 710GB.
That kinda sucks when you have 900GB to back up, no?
So yeah, you could buy another external drive and plug it into the time capsule, since I only have 1TB of space on mine (first generation) and buying a second one seems silly. having lost several lacie or other external drives over the last few years now drive redundancy is a bigger issue for me.
So, later today I will be plugging a Drobo into my Time Capsule to expand it beyond the (full) 1TB of storage in it. Going to move two 1TB drives from my HP MediaSmart server and plug in a new 2TB 'Green' Drive. I'll write up what happens when I do this but everything I've read says this works fine.
We will see.