Disk Cache Settings Recommendations

Good afternoon everyone. I'm wanting to get others opinions on what the best cache mode is for our particular setup.

Our setup is a cluster of 6 hosts with a single SSD for the proxmox install and then the VM's have a Synology RS3614xs+ for storage over NFS with a pair of SSDs for cache. Our hard disk format is qcow2.

According to the wiki, cache=none is the best option for this format and our setup. Is that still true?

Right now we have them set to writeback.

Thanks!