You can monitor NFS activity in the Analytics in Oracle ZFS Storage Appliance Analytics Guide section. This includes:
NFS operations per second
... by type of operation (read/write/...)
... by share name
... by client hostname
... by accessed filename
... by access latency
Note: When the NFS server reboots or fails over the filename is unknown at the server until a new open from the client. The file appears as unknown in Analytics worksheets.