Not that I want to push ZFS or anything, mdraid/LVM/XFS is a fine setup, but for informational purposes - ZFS can absolutely expand onto larger disks. I wasn’t aware of this until recently. If all the disks of an existing pool get replaced with larger disks, the pool can expand onto the newly available space. E.g. a RAIDz1 with 4x 4T disks will have usable space of 12T. Replace all disks with 8T disks (one after another) and your pool will have 24T of space. Replace those with 16T and you get 48T, and so on. In addition you can expand a pool by adding another redundant topology just like you can with LVM and mdraid. Finally, expanding existing RAIDz with additional disks has recently landed too.