You could use the command line program pidstat and look for the process generating the io on our system. pidstat can be called in a frequency and you may want to filter the output and condense it.
pidstat -d | sort -r -k4 | head -n20
Sort after the io reads (key 4, key 5 is writes) and give you the highest 20 values. wrap it in watch and you may find your process causing the issue.