Good timing on this thread; I have been looking into the same issue.
Often, we want to see which volumes are causing a given cluster node to have high workload, so that we can migrate high-workload volumes to another node. But OnTAP only shows volumes by vserver, making it difficult to perform node-based analysis.
I came up with the workaround of creating the symlinks in the Graphite directory tree. I agree that its a hack, but it proved the concept that you can list volumes by node and build Grafana dashboards on top of them.
In my case, I developed a Powershell script which gets all the volumes from the cluster, then generates a ksh script file to remove old symlinks and create new ones. I then have to manually copy the file to the Grafana appliance and run it. Total hack.
I am starting to look into the NMSDK in to hopes of maybe developing a Perl interface which could run natively on the Grafana appliance.
Wondering if this kind of functionality could be included in a future release of Harvest?