Cacti 1.2.19 - Disk utilization graph is not plotting anything

[bentech4u]

HI

i am not an expert in cacti and recently somehow managed to install Cacti 1.2.19.

Most of the graphs are plotting related to Linux server monitoring and only Disk utilization graph is not plotting anything. graph rrd files are created and getting updating.

can someone please help me to fix this

regards,
Ben