ZFS: "Cannot replace a replacing drive"

[Wes Morgan]

On Wed, 28 Apr 2010, Freddie Cash wrote:

> Going through the archives, I see that others have run into this issue, and
> managed to solve it via "zpool detach".  However, looking closely at the
> archived messages, all the successful tests had one thing in common:  1
> drive ONLINE, 1 drive FAULTED.  If a drive is online, obviously it can be
> detached.  In all the cases where people have been unsuccessful at fixing
> this situation, 1 drive is OFFLINE, and 1 drive is FAULTED.  As is our case:
>

What happened to the drive to fault it?