The controller card for the 7x 8TB pool. Is it flashed to ‘IT Mode’ or is it a plain HBA adapter? What is the model of the controller? Are you using Mirrors or Raid-Z(1,2,3) for the pools?
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
This resource was originally sourced from a Suggestion thread here:
https://forums.truenas.com/t/suggestion-better-svdev-planning-oversight-tools-in-gui/394/
Why consider a sVDEV?
A sVDEV has the potential to significantly speed up the operations of a spinning hard-drive (HDD) pool. One of it’s functions is to hold metadata (ZFS produces a lot of it). The other function is to make small blocks available for file storage. These small blocks are supposed to store data that is smaller than a cut…