$ 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=1280KiB/s][w=320 IOPS][eta 00m:00s]
test: (groupid=0, jobs=1): err= 0: pid=3478: Sat Jan  9 15:46:11 2021
  write: IOPS=308, BW=1236KiB/s (1266kB/s)(72.5MiB/60102msec); 0 zone resets
        [ ... ]
Run status group 0 (all jobs):
  WRITE: bw=1236KiB/s (1266kB/s), 1236KiB/s-1236KiB/s (1266kB/s-1266kB/s), io=72.5MiB (76.1MB), run=60102-60102msec
Disk stats (read/write):
    md0: ios=53/18535, merge=0/0, ticks=0/0, in_queue=0, util=0.00%, aggrios=33/18732, aggrmerge=0/0, aggrticks=143/1173174, aggrin_queue=1135748, aggrutil=96.50%
  sdd: ios=13/18732, merge=0/0, ticks=93/1123482, in_queue=1086112, util=96.09%
  sdc: ios=54/18732, merge=0/0, ticks=194/1222866, in_queue=1185384, util=96.50%