I am looking at building out a freeNAS box mostly for back ups, maybe plex, unlikely. Aim is to have somewhere to back up my proxmox server images, laptops and computers etc.

The server location is in the basement so no concerns for noise, power efficiency is important, and computer depth a limitation - 24 inches max for my rack.

Is a 4 bay unit sufficient for running in ZFS? I expect in the order of ~10 TB would be sufficient total storage. Or is 8 bay required?

What options are worth considering? Dell r530 are too deep, r510 can fit at 24 inches deep, assuming I can find one with a H330/310 controller?

TLDR:is a 4 Bay chassis provide sufficient protection for freenas ZFS with total ~ 10TB usable storage? or do I need 8 Bay?

Is a dell R320 or R510 sensible in terms of power efficiency for freenas?