How to properly link 2 ESXi?

Question

System administration

I thought that the best option for money, in order to have a large slow storage and a fast small one, is to rent two hetzner servers, one "fast" with small NVMe disks and a large amount of RAM, the second with large slow disks. I installed ESXi on both servers, installed FreeNAS on the "slow" server, assembled the disks in a mirror, connected the fast server via NFS to the slow one.
I ran into the main problem - the speed of CrystalDiskMark on a slow datastore connected via NFS is inferior to the speed even of disks connected via SMB in LAN. Secondly, when downloading a torrent to a disk connected via NFS, the speed floats endlessly from 30 to 1 MB / s, more inclined to the lower bar, the connection between the servers is gigabit. I tried without compression and deduplication - the same thing.
Should such a scheme work well at all?
What are the alternatives?