[3fe9a03ccd14ca5]

How? My understanding is that you create a new vdev and add the old vdev as a device, basically recursively creating volumes with each new device you add.

[cyphar]

Which operation are you asking about? [1] is a sister comment which I posted that outlines how to do most of the operations I mentioned.

[1]: https://news.ycombinator.com/item?id=22168494