NCQ enabled, 1 disk

1 thread
=========
heavy# zpool iostat 1
               capacity     operations    bandwidth
pool         used  avail   read  write   read  write
----------  -----  -----  -----  -----  -----  -----
...
test        40.0G   424G     75      0  9.41M      0
test        40.0G   424G     74      0  9.28M      0
test        40.0G   424G     74      0  9.28M      0
test        40.0G   424G     75      0  9.41M      0
test        40.0G   424G     76      0  9.53M      0
test        40.0G   424G     75      0  9.41M      0
test        40.0G   424G     82      0  10.3M      0
test        40.0G   424G     76      0  9.53M      0
test        40.0G   424G     73      0  9.16M      0
test        40.0G   424G     78      0  9.78M      0
test        40.0G   424G     70      0  8.79M      0
test        40.0G   424G     76      0  9.53M      0
test        40.0G   424G     77      0  9.66M      0
test        40.0G   424G     74      0  9.28M      0
test        40.0G   424G     80      0  10.0M      0
test        40.0G   424G     76      0  9.53M      0
test        40.0G   424G     78      0  9.78M      0
test        40.0G   424G     73      0  9.16M      0
test        40.0G   424G     73      0  9.16M      0
test        40.0G   424G     76      0  9.53M      0
test        40.0G   424G     74      0  9.28M      0
test        40.0G   424G     77      0  9.65M      0
test        40.0G   424G     76      0  9.53M      0
test        40.0G   424G     77      0  9.65M      0
test        40.0G   424G     71      0  8.91M      0
test        40.0G   424G     74      0  9.28M      0
test        40.0G   424G     75      0  9.41M      0
test        40.0G   424G     77      0  9.65M      0
test        40.0G   424G     79      0  9.90M      0
test        40.0G   424G     77      0  9.65M      0
test        40.0G   424G     75      0  9.41M      0
test        40.0G   424G     75      0  9.41M      0
test        40.0G   424G     71      0  8.91M      0
test        40.0G   424G     76      0  9.53M      0

16 threads
==========
heavy# zpool iostat 1
               capacity     operations    bandwidth
pool         used  avail   read  write   read  write
----------  -----  -----  -----  -----  -----  -----
...
test        40.0G   424G    119      0  15.0M      0
test        40.0G   424G    119      0  15.0M      0
test        40.0G   424G    125      0  15.7M      0
test        40.0G   424G    123      0  15.5M      0
test        40.0G   424G    124      0  15.6M      0
test        40.0G   424G    121      0  15.2M      0
test        40.0G   424G    116      0  14.6M      0
test        40.0G   424G    124      0  15.6M      0
test        40.0G   424G    125      0  15.7M      0
test        40.0G   424G    124      0  15.6M      0
test        40.0G   424G    123      0  15.5M      0
test        40.0G   424G    125      0  15.7M      0
test        40.0G   424G    123      0  15.5M      0
test        40.0G   424G    119      0  15.0M      0
test        40.0G   424G    123      0  15.5M      0
test        40.0G   424G    119      0  15.0M      0
test        40.0G   424G    129      0  16.2M      0
test        40.0G   424G    126      0  15.8M      0
test        40.0G   424G    123      0  15.5M      0
test        40.0G   424G    128      0  16.1M      0
test        40.0G   424G    122      0  15.3M      0
test        40.0G   424G    122      0  15.3M      0
test        40.0G   424G    121      0  15.2M      0
test        40.0G   424G    119      0  15.0M      0
test        40.0G   424G    122      0  15.3M      0
test        40.0G   424G    121      0  15.2M      0
test        40.0G   424G    118      0  14.9M      0
test        40.0G   424G    119      0  15.0M      0
test        40.0G   424G    123      0  15.5M      0

32 threads
==========
heavy# zpool iostat 1
               capacity     operations    bandwidth
pool         used  avail   read  write   read  write
----------  -----  -----  -----  -----  -----  -----
...
test        40.0G   424G    145      0  18.2M      0
test        40.0G   424G    138      0  17.3M      0
test        40.0G   424G    136      0  17.1M      0
test        40.0G   424G    131      0  16.5M      0
test        40.0G   424G    138      0  17.3M      0
test        40.0G   424G    142      0  17.8M      0
test        40.0G   424G    139      0  17.5M      0
test        40.0G   424G    142      0  17.8M      0
test        40.0G   424G    139      0  17.2M      0
test        40.0G   424G    143      0  17.9M      0
test        40.0G   424G    134      0  16.8M      0
test        40.0G   424G    140      0  17.6M      0
test        40.0G   424G    138      0  17.3M      0
test        40.0G   424G    135      0  17.0M      0
test        40.0G   424G    136      0  17.1M      0
test        40.0G   424G    134      0  16.8M      0
test        40.0G   424G    140      0  17.6M      0
test        40.0G   424G    136      0  17.1M      0
test        40.0G   424G    140      0  17.6M      0
test        40.0G   424G    135      0  17.0M      0
test        40.0G   424G    141      0  17.7M      0
test        40.0G   424G    147      0  18.4M      0
test        40.0G   424G    138      0  17.3M      0
test        40.0G   424G    139      0  17.5M      0
test        40.0G   424G    149      0  18.7M      0
test        40.0G   424G    134      0  16.8M      0
test        40.0G   424G    152      0  19.1M      0
test        40.0G   424G    136      0  17.1M      0

64 threads
==========
heavy# zpool iostat 1
               capacity     operations    bandwidth
pool         used  avail   read  write   read  write
----------  -----  -----  -----  -----  -----  -----
...
test        40.0G   424G    116      0  14.6M      0
test        40.0G   424G    120      0  15.1M      0
test        40.0G   424G    115      0  14.4M      0
test        40.0G   424G    119      0  15.0M      0
test        40.0G   424G    116      0  14.6M      0
test        40.0G   424G    117      0  14.7M      0
test        40.0G   424G    125      0  15.7M      0
test        40.0G   424G    114      0  14.4M      0
test        40.0G   424G    119      0  15.0M      0
test        40.0G   424G    114      0  14.3M      0
test        40.0G   424G    116      0  14.6M      0
test        40.0G   424G    117      0  14.7M      0
test        40.0G   424G    114      0  14.4M      0
test        40.0G   424G    121      0  15.2M      0
test        40.0G   424G    124      0  15.6M      0
test        40.0G   424G    116      0  14.6M      0
test        40.0G   424G    117      0  14.7M      0
test        40.0G   424G    123      0  15.5M      0
test        40.0G   424G    139      0  17.5M      0
test        40.0G   424G    144      0  18.1M      0
test        40.0G   424G    152      0  19.1M      0
test        40.0G   424G    152      0  19.1M      0
test        40.0G   424G    141      0  17.7M      0
test        40.0G   424G    143      0  17.9M      0
test        40.0G   424G    154      0  19.3M      0