You can monitor NetApp devices using our SNMP-based Network Monitoring product.
There are default device templates with performance counters for NetApp storage devices. There's also a global template for NAS which contains all NAS related performance counters common to QNAP, Synology, and NetApp vendors.
You can make use of these or create your custom templates and monitor using our custom SNMP monitoring.
Here's a partial list of performance metrics that we provide.
Do you have any specific requirements? Please let us know.