How do I see disk IO for specific ZFS file systems?

[Rudy]

I realize I can see per device iostats with zpool or gstat, but I am 
interested in specific mount points.  Is that possible?
What are the read/writes for "/tank/BBB.monkeybrains.net"?  The READS 
are low and then jump to a higher value and I'm trying to track it down.

READ/WRITE over past 6 months:
 http://www.monkeybrains.net/images/IO-past-6months.png


# zfs list
NAME                                  USED  AVAIL  REFER  MOUNTPOINT
tank                                 73.1G   368G    39K  /tank
tank/AAA.monkeybrains.net            2.54G  7.46G  2.45G  
/tank/AAA.monkeybrains.net
tank/BBB.monkeybrains.net            2.64G  97.4G  2.64G  
/tank/BBB.monkeybrains.net
tank/CCC.monkeybrains.net            1.39G  98.6G  1.39G  
/tank/CCC.monkeybrains.net


# zpool iostat -v
               capacity     operations    bandwidth
pool         used  avail   read  write   read  write
----------  -----  -----  -----  -----  -----  -----
tank        67.5G   380G     12     34   446K   257K
  mirror    67.5G   380G     12     34   446K   257K
    ad0s2       -      -      3     17   276K   258K
    ad8s2       -      -      3     17   256K   258K
----------  -----  -----  -----  -----  -----  -----


# gstat

dT: 1.001s  w: 1.000s
 L(q)  ops/s    r/s   kBps   ms/r    w/s   kBps   ms/w   %busy Name
    0     29      6    456    6.1     22    338    2.3   21.7| ad0
    0     31      8    615    9.8     22    338    2.3   19.2| ad8
    0     26      5    392    4.6     21    318    2.5    3.1| ad0s1
    0      3      1     64   13.6      1     20    2.3   19.4| ad0s2
    0     26      5    392   10.5     21    318    2.5    5.8| ad8s1
    0      5      3    224    8.7      1     20    0.3   16.9| ad8s2

specifically, I am intested in the file systems in ad0s2 and ad8s2.

Thanks if you can point me in the right direction, and thanks if you 
read this far!

Rudy