Currently sitting with 6x20tb + 2x16tb seagate exos on my main array. (112TB usable space, 2 of the disks are parity) and an additional 2x4tb wd black for my cache pool in mirror mode. Some of these disks are reaching 20k power on hours with no sign of damages on them, which is kinda impressive given my older consumer HDDs died at 5000h. I got 2 more free HDD slots on my NAS, though if I were to expand any further, I probably would go for a Disk shelf or JBOD and slot a bigger HBA into it. Also first post here, howdy from Denmark!