Comment by merlincorey

You're confusing extending vdevs with extending pools and stripes.

It's kind of apples to oranges, really.

FreeNAS documentation[0] makes it pretty clear.

In ZFS, you cannot add devices to a vdev after it has been created -- however, you CAN add more vdevs to a pool.

So basically, your complaint is that ZFS wants to have stripes of vdevs and that instead of adding 1 drive to a 3 drive RAID5 to make a 4 drive RAID5, you have to add 3 drives to a RAIDZ1 for a 6 drive RAIDZ+0 that is equivalent to a RAID50 on a hardware controller.

Yes, it's more enterprisey, but it's not especially more difficult and the result is different and perhaps better depending on your use case.