Bug#867299: [Pkg-zfsonlinux-devel] Bug#867299: zfs-dkms: Unable to expand a pool when underlying vdev has grown.

[Aron Xu]

It's not advisable to grow a pool by increasing the vdev size, but
rather you can add more vdevs to the pool to grow it in capacity, and
it would be safer for your underlying data.

Regards,
Aron