iotop - it allows the user to monitor I/O usage in the disk
To print the details of disk I/O usage
$ sudo iotop
To print processes that are actually doing disk I/O
$ sudo iotop -o
To print the output in non-interactive or batch mode
$ sudo iotop -b
To display disk I/O details of a particular process
$ sudo iotop -p <pid>
To set the number of iterations
$ sudo iotop -n 5
$ sudo iotop -n 10
To display the output with timestamp
$ sudo iotop -t
To display only the I/O usage by user home
$ sudo iotop -u
To get details of processes
$ sudo iotop -P
To display without header lines
$ sudo iotop -q
To display disk IO usage in KB
$ sudo iotop -k