Comment by chungy

> You just can't shrink them.

That's not even entirely true, though it requires shuffling around with multiple vdevs temporarily and doesn't presently support raidz. Also vdev removal is primarily made to support an accidental "oops, I added a disk I shouldn't have" rather than removing a long-lived device -- there's no technical restriction against the later case, though the redirect references could hamper performance.

The official stance has always been to send/receive to significantly change a pool's geometry where it isn't possible online.