$ 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=1480KiB/s][w=370 IOPS][eta 00m:00s]
test: (groupid=0, jobs=1): err= 0: pid=5854: Sat Jan  9 16:34:44 2021
  write: IOPS=395, BW=1581KiB/s (1618kB/s)(92.9MiB/60175msec); 0 zone resets
      [ ... ]
Run status group 0 (all jobs):
  WRITE: bw=1581KiB/s (1618kB/s), 1581KiB/s-1581KiB/s (1618kB/s-1618kB/s), io=92.9MiB (97.4MB), run=60175-60175msec
Disk stats (read/write):
    md0: ios=81/23777, merge=0/0, ticks=0/0, in_queue=0, util=0.00%, aggrios=0/11889, aggrmerge=0/0, aggrticks=0/958991, aggrin_queue=935342, aggrutil=99.13%
  sdc: ios=0/23778, merge=0/0, ticks=0/1917982, in_queue=1870684, util=99.13%
  rd0: ios=0/0, merge=0/0, ticks=0/0, in_queue=0, util=0.00%