Nick -
There's the advanced priv mode 'statit' command.
You won't find a man page for it on the support site.
'statit -b' to begin statistics collection.
Let it run for a few minutes.
'statit -e' to end and get the output.
There's a section of the output report on disk statistics.
Disks are listed by raid groups and aggrs.
Look at the ut% collumn to find hot spindles.
I hope this response has been helpful to you.
At your service,
Eugene E. Kashpureff, Sr.
Independent NetApp Consultant http://www.linkedin.com/in/eugenekashpureff
Senior NetApp Instructor, IT Learning Solutions http://sg.itls.asia/netapp
(P.S. I appreciate 'kudos' on any helpful posts.)