Proxmox and SSD issues

I run a 4 node Proxmox cluster for a Student Council.

Since our shared storage started acting up I needed to move everything to local storage. Since our budget is quite limited I threw all the harddisks we had into the ProxMox servers.

My problem now is, that the performance of the SSDs (Sata ,250gb - 2tb , different Brands, Raid 1 ZFS, enough RAM) is horrible, like 50mbit/s max write speed for movies horrible.

My assumption is that the SSDs shouldn’t permorm much worse than they would in a Windows machine, but they do. What am I doing wrong?

The node with hdds runs just fine, similar SSDs in our truenas also ran fine.