NFS kinda sucks and I'm looking for alternative solution
Rsync + cron? If you just need to backup some files/directories.
Edit: ah, saw that you will read/write a lot. Do you really need to do that over the network? Why not upload a .tar, a snapshot or whatever of the changes?
If you could be a bit more specific then maybe we could give some better advice.
Use a seedbox if you're downloading stuff and dont have enough disk space.
Ah, I see.
Perhaps sshfs could be an alternative. Not sure of the performance out of the box, but it is possible to tweak a bit.
https://www.ports.to/path/sysutils/sshfs-fuse.html