ZFS snapshot question - can I separate out some area later?

[Martin Cracauer]

I created a raidz ZFS that is mounted on /mnt/backup

It has subdirectories (not ZFS filesystems or volumes) like:
/mnt/backup/wavehh
/mnt/backup/joker
[etc]

I started taking snapshots long ago, and the snapshots are of
backup@<date>, that means top level.
NAME                  USED  AVAIL  REFER  MOUNTPOINT
backup at firstwithunk  6.85G      -   455G  -
backup at 20090922      3.75G      -   452G  -
backup at 20091022       999M      -   480G  -
backup at 200910223     2.63G      -   482G  -
backup at 20100209      9.10G      -   522G  -
backup at 20100210      2.86G      -   543G  -
backup at 20100603      26.6K      -   513G  -

Now, I want to store data there that is *not* part of future snapshots
taken in that set.  Instead the new directory should have it's own set
of snapshots, at different times.

Is that something I can still do? Given that I currently snapshotted
at top level?

If I just `zfs create`d
  /mnt/backup/recordings
and start storing data there, will that be outside the other areas's
snapshots? I tried doing this but I can't snapshot in there:
~(wings)10# zfs snapshot backup/recordings at test1
cannot create snapshot 'backup/recordings at test1': dataset is busy

%%

To clarify more, the structure now looks like this
1) /mnt/backup/wavehh	# just subdir
2) /mnt/backup/joker	# just subdir
3) /mnt/backup/newstuff	# `zfs create`d filesystem or volume

So I want 1 and 2 in the future snapshots of "backup", and newstuff
should have it's own set of snapshots.

Am I out of luck after having started to snapshot at top level?

Martin
-- 
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Martin Cracauer <cracauer at cons.org>   http://www.cons.org/cracauer/
FreeBSD - where you want to go, today.      http://www.freebsd.org/