I plan to set up a small fileserver. I already own a small server at HostEurope (VirtualServer L, 250GB space), but they don't offer enough space (there is the HostEurope Cloud, but paying for bandwidth isn't an option here, video-streaming should be possible)

Requirements summarized: Storage: > 2TB, Users: ~15, Filesizes: < 100GB, should be easily reachable (Mount as a networkdrive or at least have solid "communication" software)

My first question would be: Where can I get halfway affordable online storages? And how should I connect them to my server? Getting an additional server is a bit overkill, as I know no hoster which allows > 2 TB on a small 2 Ghz Dual Core 2 GB RAM thingy (that would be enough by far, I just need much space), and connecting it via NFS or FTP over Internet seems a bit strange and cripples performance. Do you have any advice where I could get that storage service from? (I sent HostEurope a custom request today, but they didn't answer till now. If they can provide me with that space, this question will be irrelevant, but the 2nd one is the more important one anway, don't do much more than recommend me some based on experience, you don't have to crawl hours through hosting services)

livedrive for example offers 5 TB for 17€ / month, I'd be happy with 2 TB for 20 €, the caveat is: It doesn't allow multiple users, which leads me to my second question:

Where are the security problems? Which protocol is sufficient (I want private and "public" folders etc. the usual "every user has its own and a public space"-thing), secure and fast? (I'd tend to (S)FTP, problem with FTP is: Most of those hosting services don't even allow FTP with mutliple users and single users lead me into "hacking" a solution (you could map the basic folder structure on the main server and just mount every subfolder from the storage, things get difficult with a public folder with 644 permissions though)

Is useing something like PKI or 802.1X overkill for private uses?