Many people would say why don't you use rsync? rsync is, in deed, a wonderful little tool that has a lot of features, but it doesn't support segmented file transfer. Well, there are a lot of software applications out there that can handle segmented file transfers over FTP or HTTP protocol. One of them is prozilla. But, as rsync, prozilla doesn't support SFTP protocol. So, how can we handle this? The answer has four letters: lftp. Quote from lftp man page:
Gets the specified file using several connections. This can speed up transfer, but loads the net and server heavily impacting other users. Use only if you really have to transfer the file ASAP
lftp sftp://user[:password]@host.ro[:port] -e "mirror -c --parallel=5 --use-pget-n=5 \"/path/to/folder/\""
Very simple and effective, right?