These are mine backup boxes based on FreeBSD with ZFS and rsnc(1) for the transfer layer.

For the hardware I use MiniITX motherboards with low power 6W TDP CPU.

Disks are 2.5 4TB or 5TB in mirror on not depending in the needs.

- https://vermaden.wordpress.com/2019/04/03/silent-fanless-fre...

- https://vermaden.wordpress.com/2018/08/28/silent-fanless-fre...

Regards.