You should be able to use an application called rsync.
yum -y install rsync
There should be something in there about SFTPing directly into the remote server and transferring the files. I don't have that much experience with it since I typically use r1.
Hope this helps!
I have had a quick look at this in ssh and I dare not touch anything as I don't want to mess the server up as it describes about moving the whole folder including passwords, ftps etc. I don't honestly know what the /vz folder is used for all I know is that is where all the space I was meant to have been supplied with my server has been dumped and I just want to move it out of there into the / folder so it can be used.
What do you want to use the server for? It seems from what little information you posted it is setup to host VPS machines which will live in the /vz directory. If you want to host VPS on here just create them in the /vz directory and you can use all of the space on that partition.
If you want to do something else with the machine what is it, and where do you specifically need more space? Another option which might be easier is just creating symlinks to the /vz partition from where you are running out of space.