many people just buy junk like this https://www.amazon.com/Mikrotik-Router-Switch-CRS305-CRS305-1G-4S/dp/B08437RDM1 it’s cheaper in the long run.

You will need a good 10Gb nic, I have been using Intel nic’s if you use a Intrusion Prevention System that can eat away at the CPU, also more RAM helps like 8GB’s or more for IPS, I use 16GB’s for IPS + ZFS and a nice Switch can help a lot as it can do DNS and the works, more or less i use a firewall box to a Switch and use a Layer 3 Switch for routing, some can do 20+Gb’s routing.

on my NAS i do and work data as well.

Proxmox, TrueNAS, Debian with cockpit etc. really any type 1 hyperviser work’s.

Maybe your HBA is having issues? or a Drive is Failing? have you done a memtest? you may need to do system wide tests, it can even be a PSU failing or a software Bug.

also TrueNAS is built with Docker they use it heavily something like 106 apps, Debian has good ZFS support, but you will end up doing a lot of unneeded work using Debian unless you keep it simple.

ZFS is by far the best just use TrueNAS, Ubuntu is crap at supporting ZFS, also only set your pool’s VDEV 6-8 wide.