The attached dashboard is useful in seeing the impact of QoS policies on volume I/O, and current volume I/O relative to the past 2 weeks.
It shows the range of activity and the mean for iops/latency/throughput by time of day for the past N days. It superimposes the current day/period's values on this and then shows the latency breakdown by these service centers. I use this to demonstrate to users, the impact that a given qos policy is having on their volume(s).

Since we're adding to your feature request list Chris, what I'd find really useful is to be able to add to this dashboard would be:
- Number of samples in which latency_from_throttle (DELAY_CENTER_QOS_LIMIT) is non-zero in a given period of X samples.
- Either aggregated by harvest into a rate of some sort, or just a counter that I could do T2 - T1 to get a value for a period.
- IE: The number of minutes in which some throttling of the volume has taken place over the range in question.
[EDIT] It turns out that we can do this in graphite using built in functions because of a piece of grade school math that I should have remembered before posting. SUM / AVG = COUNT
We DO have sum and avg functions in Graphite.
A: summarize(netapp.perf.$Group.$Cluster.svm.$SVM.vol.$Volume.qos_latency_from_throttle, '1h', 'sum', false)
B: summarize(netapp.perf.$Group.$Cluster.svm.$SVM.vol.$Volume.qos_latency_from_throttle, '1h', 'avg', false)
C: alias(divideSeries(#A, #B), 'Throttled samples')
I'm still amazed by how much we can do using Harvest + Graphite.