Nice, this is a feature that'll really improve ZFS's usability for me, as a home user. I'd like to be able to redo my Zpool with a different architecture (6xDisks in RaidZ2 rather than 4x in RaidZ1). Doing it online rather than as a copy would be awesome. The next best thing would be online ZVol restructuring, though.
I don't think this will do what you want. One limitation is:
Currently, device removal only works if all top
level vdevs are plain disks / files. At the very
least, we want to make device removal interact
intelligently with mirrored disks.
I think that statement means that this feature will not work with mirrored or RaidZ* configurations.
