Well… two things:
$ iostat -dmx 5
This will give you the running avg usage details of your disks.
Look for:
r/s - read ops per sec
w/s - write ops per sec
right most column, is a calculated indication in % of drive busy
First two can be combined for total drive IOPS.
500 is a very large number… if you are to use this setting at all, use low sensible numbers. It’s a limitation setting, it can’t force more traffic to your node if you set it high 