As a little update to an older post on this subject, and although this post from Matthew Ahrens is about the new scrub code recently introduced in OpenSolaris build 94–and was in fact a priority before the launch of the Sun Storage 7000 Unified Storage Systems (a.k.a. Amber Road)–it is interesting to note that some of the new code will be usable to remove a disk from a ZFS pool.
As Matthew wrote:
This work lays a bunch of infrastructure that will be used by the upcoming device removal feature.