I successfully recreated the zpool from scratch (it's an rsync backup of
my NAS), and then ran new rsyncs. Getting these rsyncs running was a bit
of a nightmare. Once I got a run successfully going, one drive kept
dropping out, putting the zpool offline. Well, that explained a few
problems,
As that link was to a post of mine, I'll play closer attention to the thread.
I don't recall the details, but in general, my recollection is that various
tools were incorrectly setting or reporting the label information.
ZFS puts labels at both ends of the disk and will get seriously befuddled
