Hardware
24 drive bay case
4TB drives, all same make/model/etc.
Possible ZFS configurations, arranged by number of disks
20 disks
raidz2 = 1 zpool, 2 vdevs of 10 disks, 2 can fail per vdev, 4 can fail in total
32TB per vdev, 64TB total usable, 20% of total drives can fail
22 disks
raidz3 = 1...