Time for the Basics…or reaching out to iX Systems for hardware and advice.
Only thing to note is block storage, iSCSI, is recommended to keep pool below 50% full usage.
BASICS
iX Systems pool layout whitepaper
https://www.truenas.com/solution-guides/#TrueNAS-PDF-zfs-storage-pool-layout/11/
Special VDEV (sVDEV) Planning, Sizing, and Considerations
