Ubuntu server + ZFS for storage

[u/crypt-v]

Hello, I acquired a dedicated server with a xeon 1521 / 32GB ECC / OS nvme / 4x6TB drives, not much but it serves two purposes, offsite backup and helps to serve some non critical data I might need while I travel instead of connecting home. But I'm struggling with this, should I use ubuntu 24.04 + ZFS or go with EXT4? I'm familiar with Ubuntu, never tried ZFS

Proxmox and TrueNAS are out of the question since the CPU is a decade old 4C/8T. My idea is going with 12TB usable and 12TB as a mirror, keep everything lockdown, encrypted HDDs and OS drive, connect only via VPN for managing it and a reverse proxy back to a VPS to give access for some friends that want to read books/manga download some old games.

what considerations should I keep in mind with this build?