NCQ disabled, 2 disks, 32 threads

heavy# zpool iostat 1
               capacity     operations    bandwidth
pool         used  avail   read  write   read  write
----------  -----  -----  -----  -----  -----  -----
...
test        40.0G   888G    124      0  13.6M      0
test        40.0G   888G    234      0  28.6M      0
test        40.0G   888G    233      0  29.0M      0
test        40.0G   888G    232      0  29.1M      0
test        40.0G   888G    230      0  28.7M      0
test        40.0G   888G    230      0  28.8M      0
test        40.0G   888G    236      0  29.5M      0
test        40.0G   888G    221      0  27.5M      0
test        40.0G   888G    226      0  28.3M      0
test        40.0G   888G    233      0  29.2M      0
test        40.0G   888G    234      0  29.3M      0
test        40.0G   888G    230      0  28.8M      0
test        40.0G   888G    217      0  27.0M      0
test        40.0G   888G    226      0  28.3M      0
test        40.0G   888G    237      0  29.7M      0
test        40.0G   888G    233      0  29.2M      0
test        40.0G   888G    240      0  29.9M      0
test        40.0G   888G    233      0  29.2M      0
test        40.0G   888G    238      0  29.8M      0
test        40.0G   888G    233      0  29.0M      0
test        40.0G   888G    222      0  27.8M      0
test        40.0G   888G    232      0  29.1M      0
test        40.0G   888G    232      0  29.1M      0
test        40.0G   888G    232      0  29.1M      0
test        40.0G   888G    224      0  28.1M      0
test        40.0G   888G    233      0  29.2M      0
test        40.0G   888G    243      0  30.3M      0
test        40.0G   888G    233      0  29.2M      0
test        40.0G   888G    230      0  28.8M      0
test        40.0G   888G    226      0  28.3M      0
test        40.0G   888G    235      0  29.5M      0
test        40.0G   888G    231      0  29.0M      0
test        40.0G   888G    236      0  29.6M      0
test        40.0G   888G    226      0  28.2M      0
test        40.0G   888G    230      0  28.8M      0
test        40.0G   888G    225      0  28.1M      0
test        40.0G   888G    236      0  29.6M      0
test        40.0G   888G    222      0  27.8M      0
test        40.0G   888G    236      0  29.6M      0
test        40.0G   888G    235      0  29.3M      0
test        40.0G   888G    233      0  29.2M      0
test        40.0G   888G    229      0  28.7M      0
test        40.0G   888G    232      0  29.1M      0
test        40.0G   888G    234      0  29.3M      0
test        40.0G   888G    232      0  29.1M      0
test        40.0G   888G    228      0  28.6M      0
test        40.0G   888G    221      0  27.7M      0
test        40.0G   888G    231      0  29.0M      0
test        40.0G   888G    230      0  28.8M      0
test        40.0G   888G    227      0  28.5M      0
test        40.0G   888G    231      0  29.0M      0
test        40.0G   888G    235      0  29.5M      0
test        40.0G   888G    241      0  30.2M      0
test        40.0G   888G    233      0  29.2M      0
test        40.0G   888G    235      0  29.5M      0
test        40.0G   888G    229      0  28.7M      0
test        40.0G   888G    224      0  28.1M      0
test        40.0G   888G    229      0  28.7M      0
test        40.0G   888G    237      0  29.7M      0
test        40.0G   888G    227      0  28.5M      0
test        40.0G   888G    233      0  29.2M      0
test        40.0G   888G    232      0  29.1M      0
test        40.0G   888G    242      0  30.3M      0
test        40.0G   888G    239      0  30.0M      0
test        40.0G   888G    224      0  28.1M      0
test        40.0G   888G    234      0  29.3M      0
test        40.0G   888G    226      0  28.3M      0
test        40.0G   888G    219      0  27.5M      0
test        40.0G   888G    237      0  29.7M      0
test        40.0G   888G    227      0  28.5M      0
test        40.0G   888G    229      0  28.7M      0
test        40.0G   888G    233      0  29.2M      0
test        40.0G   888G    238      0  29.8M      0
test        40.0G   888G    228      0  28.6M      0
test        40.0G   888G    229      0  28.7M      0
test        40.0G   888G    222      0  27.8M      0
test        40.0G   888G    240      0  30.1M      0
test        40.0G   888G    230      0  28.8M      0
test        40.0G   888G    221      0  27.7M      0
test        40.0G   888G    216      0  27.1M      0
test        40.0G   888G    233      0  29.2M      0
test        40.0G   888G    231      0  29.0M      0
test        40.0G   888G    221      0  27.7M      0
test        40.0G   888G    231      0  29.0M      0
test        40.0G   888G    235      0  29.5M      0
test        40.0G   888G    220      0  27.6M      0
test        40.0G   888G    232      0  29.1M      0
test        40.0G   888G    211      0  26.5M      0
test        40.0G   888G    233      0  29.2M      0
test        40.0G   888G    229      0  28.7M      0
test        40.0G   888G    233      0  29.2M      0
test        40.0G   888G    231      0  29.0M      0
test        40.0G   888G    228      0  28.6M      0
test        40.0G   888G    231      0  29.0M      0
test        40.0G   888G    223      0  28.0M      0
test        40.0G   888G    229      0  28.7M      0
test        40.0G   888G    231      0  29.0M      0
test        40.0G   888G    231      0  29.0M      0
test        40.0G   888G    227      0  28.5M      0
test        40.0G   888G    231      0  29.0M      0
test        40.0G   888G    225      0  28.2M      0
test        40.0G   888G    229      0  28.7M      0
test        40.0G   888G    229      0  28.7M      0
test        40.0G   888G    230      0  28.8M      0
test        40.0G   888G    225      0  28.2M      0
test        40.0G   888G    227      0  28.5M      0
test        40.0G   888G    241      0  30.2M      0
test        40.0G   888G    233      0  29.2M      0
test        40.0G   888G    228      0  28.6M      0
test        40.0G   888G    236      0  29.6M      0
test        40.0G   888G    233      0  29.2M      0
test        40.0G   888G    239      0  30.0M      0
test        40.0G   888G    226      0  28.3M      0
test        40.0G   888G    228      0  28.6M      0
test        40.0G   888G    236      0  29.6M      0
test        40.0G   888G    229      0  28.7M      0
test        40.0G   888G    222      0  27.8M      0
test        40.0G   888G    226      0  28.3M      0
test        40.0G   888G    230      0  28.8M      0
test        40.0G   888G    230      0  28.8M      0
test        40.0G   888G     49      0  6.19M      0