Even with 16TB disks I would not worry about 12 or 15 disk vdevs running in raidz3. Which is to say, beat the shit out of the disks before deploying them[1] to

Even with 16TB disks I would not worry about 12 or 15 disk vdevs running in raidz3. Which is to say, beat the shit out of the disks before deploying them[1] to weed out early failures, then aggressively fail them out at the first sign of trouble[2]. We don't use hot spares - we just very aggressively pull drives that give us any meaningful smart errors ... [1] perhaps with the badblocks tool ... [2] smartctl