You could use bcachefs on the OSD drives, but you can also just point the WAL/DB of the OSD to a partition on the ssd and have the data on hdd. You don't have t

You could use bcachefs on the OSD drives, but you can also just point the WAL/DB of the OSD to a partition on the ssd and have the data on hdd. You don't have to tier pools to get help with small writes/metadata using ssds.