[CentOS] I/o Read/write BYTes ?

> 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)