using iostat from systat package?
sudo yum install sysstat (not the two 's' in the middle)
For example: iostat -m 5 /dev/md{0,1} /dev/sd{a,b,c,d,e}
-m : output in megabytes 5: every 5s /dev/md{0,1} /dev/sd{a,b,c,d,e} : the various drives to filter (no such argument will show them all)