> You lose usable space not putting all your drives into a single parity array Well if you're aiming for a specific ratio but want greater capacity without upg

> You lose usable space not putting all your drives into a single parity array Well if you're aiming for a specific ratio but want greater capacity without upgrading all disks to larger capacities, your only option is to use more vdevs configured just the same. Example: 66% usable capacity, 6 disks in a raidz2 (4 usable + 2 parity) or 9 disks in a raidz3 (6 usable + 3 parity). If you want to add capacity but maintain your parity ratio (for a given fault tolerance risk) there is no raidzN with N > 3, so you must add vdev. Increasing the size of the raidz vdev means you're reducing your failure tolerance.