Found this nice post on good commands to know appart from the obvious top
Basically they are
top
and
vm_stat 5
and
iostat -d -K -w 5
and
sudo fs_usage -f filesys
and
sudo iotop -C 5 10
# or
sudo iotop -P -C 5 10
# or
sudo iotop -Pm /
Examples for iotop and fs_usage from osdaily.