I'm new to FreeNAS, and I'm still researching before I actually attempt my first build. Anyway, I think I understand the relation between Zpools, Vdevs, and individual drives, but one doubt remains: suppose I have a Zpool consisting of a single Vdev, which in turn consists of 4 drives using Raid-Z2. Suppose also that initially all drives are 3TB drives. Since I cannot grow a Z2 Vdev by adding more drives, the only way the storage in this Vdev can grow is by increasing the capacity of each drive, right? But suppose I replace the drives one by one as each drive fails, and the replacements will be 4TB drives. Does the capacity of the pool only actually increase when the last 3TB drive is replaced by a 4TB one? Or is Raid-Z2 smarter than this and can already start taking advantage of the extra capacity after the first, second, and third replacements?