You should look into FTP packages first. Here are a couple that might work for you <a href=”http://www.grouplogic.com/products/masstransit/”>MassTransit</a> or <a href=”http://www.g6ftpserver.com/”>Gene6 FTP</a>
Since this sound like it will be your only server, you should get a moderately beefy server with a good deal of redundant drives and storage.
Check out the free <a href=”http://filezilla-project.org/”>Filezilla FTP client & server</a>. Surely a person would not use FTP to transfer 100gigs of data?? That would take a LOT of time and bandwidth. It would likely interfere with other clients. If a client has that much data to transfer, you may need a dedicated connection just for that client.
Did you end u choosing colocating? Or did you use a service provider? Just curious. 100gb is a lot of data to transfer via ftp.
We basically burn it on disks , and then ship those disks around.