Sharing Chris reply for displaying 7mode filer volume used size graph ,
This graph is not pre-defined ,can duplicate existing IOP graph and remove other metrics ,add below metric
here is the metric to use
scale(netapp.perf7.$Group.$Node.vol.$Volume.wv_fsinfo_blks_used, 0.0009765625)
I do have 7-mode vol used though, collecting directly from the filer, as part of the IOP density graph. Find this graph on the 7-mode volume dashboard. It is the counter called “wv_fsinfo_blks_used” and displays the volume used (active filesystem + snap). It is normalized to Mbytes, so if you want in Gigabytes you could add a new graph with this metric string:
scale(netapp.perf7.$Group.$Node.vol.$Volume.wv_fsinfo_blks_used, 0.0009765625)