iotop
Display a table of current I/O usage by processes or threads.
TLDR
Start top-like I/O monitor
$ iotop
Show only processes or threads actually doing I/O
$ iotop -o
Show I/O usage in non-interactive mode
$ iotop -b
Show only I/O usage of processes(Default is to show all threads)
$ iotop -P
Show I/O usage of given PID(s)
$ iotop -p [PID]
Show I/O usage of a given user
$ iotop -u [user]
Show accumulated I/O instead of bandwidth
$ iotop -a