$ sudo fio --bs=4k --ioengine=libaio --iodepth=32 --size=10g --direct=1 --runtime=60 --filename=/dev/md0 --rw=randwrite --numjobs=1 --name=test
test: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=libaio, iodepth=32
fio-3.12
Starting 1 process
Jobs: 1 (f=1): [w(1)][100.0%][w=1305KiB/s][w=326 IOPS][eta 00m:00s]
test: (groupid=0, jobs=1): err= 0: pid=5941: Sat Jan  9 16:38:30 2021
  write: IOPS=325, BW=1301KiB/s (1333kB/s)(76.4MiB/60156msec); 0 zone resets
       [ ... ]
Run status group 0 (all jobs):
  WRITE: bw=1301KiB/s (1333kB/s), 1301KiB/s-1301KiB/s (1333kB/s-1333kB/s), io=76.4MiB (80.2MB), run=60156-60156msec
Disk stats (read/write):
    md0: ios=82/19571, merge=0/0, ticks=0/0, in_queue=0, util=0.00%, aggrios=0/13048, aggrmerge=0/0, aggrticks=0/797297, aggrin_queue=771080, aggrutil=97.84%
  sdd: ios=0/19572, merge=0/0, ticks=0/1658959, in_queue=1619688, util=93.01%
  sdc: ios=0/19572, merge=0/0, ticks=0/732934, in_queue=693552, util=97.84%
  rd0: ios=0/0, merge=0/0, ticks=0/0, in_queue=0, util=0.00%