NCQ disabled, 16 disks, 32 threads

heavy# zpool iostat 1
               capacity     operations    bandwidth
pool         used  avail   read  write   read  write
----------  -----  -----  -----  -----  -----  -----
...
test        40.0G  7.21T    452      0  54.9M      0
test        40.0G  7.21T  1.46K      0   187M      0
test        40.0G  7.21T  1.48K      0   189M      0
test        40.0G  7.21T  1.51K      0   194M      0
test        40.0G  7.21T  1.48K      0   189M      0
test        40.0G  7.21T  1.43K      0   183M      0
test        40.0G  7.21T  1.41K      0   180M      0
test        40.0G  7.21T  1.51K      0   194M      0
test        40.0G  7.21T  1.45K      0   186M      0
test        40.0G  7.21T  1.42K      0   182M      0
test        40.0G  7.21T  1.44K      0   184M      0
test        40.0G  7.21T  1.41K      0   180M      0
test        40.0G  7.21T  1.46K      0   187M      0
test        40.0G  7.21T  1.45K      0   186M      0
test        40.0G  7.21T  1.46K      0   186M      0
test        40.0G  7.21T  1.42K      0   181M      0
test        40.0G  7.21T  1.43K      0   183M      0
test        40.0G  7.21T  1.42K      0   182M      0
test        40.0G  7.21T  1.49K      0   191M      0
test        40.0G  7.21T  1.41K      0   181M      0
test        40.0G  7.21T  1.47K      0   188M      0
test        40.0G  7.21T  1.47K      0   188M      0
test        40.0G  7.21T  1.48K      0   189M      0
test        40.0G  7.21T  1.44K      0   184M      0
test        40.0G  7.21T  1.47K      0   188M      0
test        40.0G  7.21T  1.50K      0   191M      0
test        40.0G  7.21T  1.43K      0   184M      0
test        40.0G  7.21T  1.45K      0   185M      0
test        40.0G  7.21T  1.47K      0   189M      0
test        40.0G  7.21T  1.36K      0   174M      0
test        40.0G  7.21T  1.42K      0   181M      0
test        40.0G  7.21T  1.48K      0   189M      0
test        40.0G  7.21T  1.42K      0   181M      0
test        40.0G  7.21T  1.48K      0   189M      0
test        40.0G  7.21T  1.50K      0   192M      0
test        40.0G  7.21T  1.41K      0   180M      0
test        40.0G  7.21T  1.48K      0   189M      0
test        40.0G  7.21T  1.47K      0   188M      0
test        40.0G  7.21T  1.42K      0   182M      0
test        40.0G  7.21T  1.43K      0   184M      0
test        40.0G  7.21T  1.44K      0   184M      0
test        40.0G  7.21T  1.41K      0   180M      0
test        40.0G  7.21T  1.48K      0   189M      0
test        40.0G  7.21T  1.47K      0   189M      0
test        40.0G  7.21T  1.47K      0   188M      0
test        40.0G  7.21T  1.43K      0   183M      0
test        40.0G  7.21T  1.42K      0   182M      0
test        40.0G  7.21T  1.45K      0   185M      0
test        40.0G  7.21T  1.42K      0   181M      0
test        40.0G  7.21T  1.45K      0   186M      0
test        40.0G  7.21T  1.41K      0   180M      0
test        40.0G  7.21T  1.46K      0   188M      0
test        40.0G  7.21T  1.41K      0   180M      0
test        40.0G  7.21T  1.39K      0   178M      0
test        40.0G  7.21T  1.44K      0   184M      0
test        40.0G  7.21T  1.42K      0   182M      0
test        40.0G  7.21T  1.42K      0   181M      0
test        40.0G  7.21T  1.48K      0   190M      0
test        40.0G  7.21T  1.44K      0   184M      0
test        40.0G  7.21T  1.44K      0   184M      0
test        40.0G  7.21T  1.39K      0   178M      0
test        40.0G  7.21T  1.37K      0   175M      0
test        40.0G  7.21T  1.43K      0   183M      0
test        40.0G  7.21T  1.38K      0   177M      0
test        40.0G  7.21T  1.44K      0   184M      0
test        40.0G  7.21T  1.38K      0   177M      0
test        40.0G  7.21T  1.44K      0   184M      0
test        40.0G  7.21T  1.45K      0   186M      0
test        40.0G  7.21T  1.45K      0   185M      0
test        40.0G  7.21T  1.42K      0   182M      0
test        40.0G  7.21T  1.47K      0   188M      0
test        40.0G  7.21T  1.42K      0   182M      0
test        40.0G  7.21T  1.41K      0   180M      0
test        40.0G  7.21T  1.46K      0   187M      0
test        40.0G  7.21T  1.41K      0   180M      0
test        40.0G  7.21T  1.46K      0   186M      0
test        40.0G  7.21T  1.45K      0   185M      0
test        40.0G  7.21T  1.44K      0   185M      0
test        40.0G  7.21T  1.46K      0   187M      0
test        40.0G  7.21T  1.35K      0   173M      0
test        40.0G  7.21T  1.40K      0   179M      0
test        40.0G  7.21T  1.45K      0   186M      0
test        40.0G  7.21T  1.47K      0   189M      0
test        40.0G  7.21T  1.36K      0   174M      0
test        40.0G  7.21T  1.45K      0   186M      0
test        40.0G  7.21T  1.42K      0   182M      0
test        40.0G  7.21T  1.45K      0   186M      0
test        40.0G  7.21T  1.37K      0   176M      0
test        40.0G  7.21T  1.41K      0   180M      0
test        40.0G  7.21T  1.40K      0   179M      0
test        40.0G  7.21T  1.45K      0   186M      0
test        40.0G  7.21T  1.42K      0   182M      0
test        40.0G  7.21T  1.38K      0   177M      0
test        40.0G  7.21T  1.44K      0   184M      0
test        40.0G  7.21T  1.47K      0   188M      0
test        40.0G  7.21T  1.43K      0   183M      0
test        40.0G  7.21T  1.44K      0   184M      0
test        40.0G  7.21T  1.46K      0   187M      0
test        40.0G  7.21T  1.40K      0   180M      0
test        40.0G  7.21T  1.47K      0   189M      0
test        40.0G  7.21T  1.40K      0   180M      0
test        40.0G  7.21T  1.45K      0   185M      0
test        40.0G  7.21T  1.42K      0   182M      0
test        40.0G  7.21T  1.44K      0   184M      0
test        40.0G  7.21T  1.42K      0   181M      0
test        40.0G  7.21T  1.41K      0   181M      0
test        40.0G  7.21T  1.41K      0   180M      0
test        40.0G  7.21T  1.41K      0   181M      0
test        40.0G  7.21T  1.42K      0   182M      0
test        40.0G  7.21T  1.44K      0   184M      0
test        40.0G  7.21T  1.45K      0   186M      0
test        40.0G  7.21T  1.42K      0   181M      0
test        40.0G  7.21T  1.38K      0   176M      0
test        40.0G  7.21T  1.38K      0   177M      0
test        40.0G  7.21T  1.45K      0   185M      0
test        40.0G  7.21T  1.46K      0   187M      0
test        40.0G  7.21T  1.44K      0   184M      0
test        40.0G  7.21T  1.44K      0   184M      0
test        40.0G  7.21T  1.46K      0   187M      0
test        40.0G  7.21T  1.40K      0   179M      0
test        40.0G  7.21T    387      0  48.4M      0