ONTAP v9 bugThere is a problem with ONTAP v9 firmware which however might not affect all v9 instances.
Storage firmware reporting very high utilization peaks randomly for different volumes/aggregates/port etc.
There is logged a call (2006765793) with NetApp and the problem is under investigation.
Latest new as per July 2017 is that it is registered bug 1091745.
The fix is not included yet in 9.1P5.
It will be included in some further patch release, it is not clear which one yet.
Note: The bug does not affect NetApp performance, it just reporting wrong numbers time to time (we would say that some performance data counters simple overflow).
We are not sure if this affects all 9.x firmwares and users. For example our lab machine is unaffected. Just a few users has reported it.