ZFS zpool mirror drive replacement confusion

[Martin Cracauer]

My computer keeps doing what I say, not what I want :-)

This zpool with a 2-drive mirror had a dead drive (ad10) which I
removed.  After I tried to put ad2 as a replacement drive I ended up
with the drive not in the mirror, it seems to have extended the zpool
(it's size?).

        NAME        STATE     READ WRITE CKSUM
        cbackup3    DEGRADED     0     0     0
          mirror    DEGRADED     0     0     0
            ad6     ONLINE       0     0     0
            ad10    REMOVED      0     0     0
          ad2       ONLINE       0     0    11

Unfortunately I didn't keep note of the specific command that I used.

Two questions:

- Does somebody know offhand what I did and what I should have done
  instead to get ad2 into the mirror?

- Would there have been a way to remove ad2 from this set? It didn't
  let me, saying it can only remove drives from mirror or raid sets.
  I think it should have been possible before I mounted the filesystem
  in there read-write for the first time after the drive add.  This
  seems like an easy mistake to make.

The array doesn't contain important data, just trying to sort out
things for the future.

Martin
-- 
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Martin Cracauer <cracauer at cons.org>   http://www.cons.org/cracauer/