Thanks for all the tips and advice. At home, I use a Lenovo Y580 (is it 15" or 17" wide?) with a USB hub connected to two external 1 terabyte hard drives containing two identical sets of backups. Each (identical) set comprises of about 600GB of files, including personally made movies etc. I don't have to access this archive every day. But as soon as I unhook the Lenovo and travel somewhere, I suddenly need the archive. Usually both external drives were left at home, unless of course I've taken one of them along. The Lenovo is quite big and heavy so I've been dreaming about the Surface Pro 2. It would seem that the only solution would be to keep taking one of the two 1 terabyte external hard drives along. Nothing I've read above will save me from that, it would seem. I don't agree at all that the Surface Pro should be viewed as a little world on its own, a mere "tablet" separated from other computer equipment and computer needs you might have. If it does not slot into everything easily, then it needs more development. Any details about the docking station available?
Alright, your use case is a bit unique, but if you do find that you need your video production archives and whatever, that makes sense why you need constant large storage. And no, I wouldn't say Surface Pro is mostly a tablet either; it's a true hybrid, and with the upcoming dock, would better fit the "primary device" use case. People get by with USB docks and plugging a few cables now, but the dock looks like a slick solution. Too bad it won't be out for the holiday season. It's the Surface RT-class devices that are pure satellite (although I've read that some people treat it as a primary, so good for them).
Let's do the maths. $0.6 cents a day puts a hole in your pocket? Really?
You're missing the point. SkyDrive in paid form is for dynamic data use across devices. You really would not want to ARCHIVE masses of data for
long-term rental storage in this manner. We're talking about years, decades. That's supremely inefficient use of resources. I use the free minimum for certain backups, but mostly to sync documents between Surface and desktop. Besides, I wouldn't treat cloud storage on someone else's server as particularly safe for my archive data.
In the US it is $60/year for 100GB of SkyDrive Storage so 600GB would be $360/year. I would get a 2.5" 1TB USB 3.0 Portable Drive honestly....
This is really the only practical solution for OP. Buy the cheapest Surface Pro 2 and get a portable external drive (cheaper than upgrading to 512GB, that's for sure). Encrypt both if necessary. Even the portable drive combined with a SPro2 would probably be lighter than your Lenovo, I'm guessing.
Edit to add: Ultramobile laptops with SSD drives in general aren't going to have more than 512GB in space at a reasonable price point anyway. I don't know where these sit right now in the market, but you could look into dual drive utlrabooks (or, again just other ultramobile laptops with HDD).
(Though it starts at 15GB.) Under no circumstances is your data truly safe "indefinitely" while on a third party's servers. Websites get hacked. Copy had a nice backdoor that made client data viewable, discovered earlier this year (fortunately closed). 
