Network storage application
Maybe you could try webdav with apache, and davfs2 on the client side. This should be about the same speed as FTP.

NFS is also an option, if your kernel supports it. However, if you want some security (neither of these options has encryption (ok, webdav can run over http), but at least authentication), nfs authentication is pretty hard to set up compared to webdav.

If you want some real security, you can use SFTP/sshfs, and fiddle with the SFTP's encryption settings, namely the set the Ciphers and MACs options (you have to set these client-side). There is probably a combination that is significantly faster, and any is still much more secure than nothing.

And for any of these, I would use some chroot-ed linux with native code, e.g. debian (it's quite easy to install with Lil'debi).