I have a situation in which Resource Monitor shows 100 - 400 ms disk Response Time (latency) for various processes in the Disk-Disk Activity tab.   

Resource Monitor doesnt break Response Time down into read/write/other so I hopped over to perfmon.    I enabled the following perfmon metrics for the block device showing 100 - 400ms response time in Resource Monitor:

Physical Disk:

Avg. Disk Bytes/Read

Avg. Disk Bytes/Write

Avg. Disk Bytes/Transfer

Physical Disk:

Avg. Disk sec/Read

Avg. Disk sec/Write

Avg. Disk Sec/Transfer

Those permon counters were chosen to have a look at block size and latency.   Perfmon reported very large values for Avg. Disk Bytes/Read (up to 500,000) which may explain some of the higher Response Time numbers in Resource Monitor.    HOWEVER, perfmon showed  very low numbers for Avg. Disk sec/Read whereas Resource Monitor showed 100 - 400 ms.  

Does anybody know what might account for the difference in Response Times between perfmon and Resource Monitor?   Specifically, the difference between Avg. Disk sec/Transfer (perfmon) and the Response Time column in Resource Monitor?

Windows Server 2008, Exchange 2010, NetApp v3250 running 8.1.4P3 7-Mode.  All LUNS presented via iSCSI.

-Phil