Comment by ryao
5 days ago
There is a clever trick that is used to make top level removal work. The code will make the vdev readonly. Then it will copy its contents into free space on other vdevs (essentially, the contents will be stored behind the scenes in a file). Finally, it will redirect reads on that vdev into the stored vdev. This indirection allows you to remove the vdev. It is not implemented for raid-z at present though.
Though the vdev itself still exists after doing that? It just happens to be backed by, essentially, a "file" in the pool, instead of the original physical block devices, right?
Yes.