How does the Netapp or DFM measure volume and lun latency?  Does it just measure how long it's taking to service requests from the back ports to the front ports?  Or does it measure some sort of fibre ping to the host?

I am looking in the management console in DFM/Ops Mgr and seeing spikes of very high volume and lun latency (seconds...) on an N-Series IBM gateway filer.  I've looked at all the usual suspects, including misaligned VMs, high correlated IOPs, delays on the backend disk, deferred consistency points.  Nothing is matching up.  Most of the connected systems are on a Cisco UCS with NPIV.  The systems with the lowest IOs have the highest latency numbers.

Thoughts?

TIA,

Fred