Hi All,
Thought I would post this here as it's an issue I had and took awhile to get the information needed to get to the bottom of it!
Issue I had was the percentage of discards on Solarwinds was reporting as 30-40% but when you logged onto the switch and did the calculation from the CLI figures it was was less 1%.
The percentage of discards or errors is calculated as follows on Solarwinds:
((InterfaceErrors.In_Discards + InterfaceErrors.Out_Discards) / (InterfaceErrors.In_Errors + InterfaceErrors.Out_Errors + InterfaceErrors.In_Discards + InterfaceErrors.Out_Discards + InterfaceTraffic.In_TotalPackets + InterfaceTraffic.Out_TotalPackets))*100
Polled OIDs:
ifInDiscards = "1.3.6.1.2.1.2.2.1.13
ifInErrors = "1.3.6.1.2.1.2.2.1.14"
ifOutDiscards = "1.3.6.1.2.1.2.2.1.19"
ifOutErrors = "1.3.6.1.2.1.2.2.1.20"
TotalPackets are calculated as SUM of: (64bit counters)
ifHCInUcastPkts = "1.3.6.1.2.1.31.1.1.1.7" + ifHCInNUcastPkts = "1.3.6.1.2.1.31.1.1.1.8"
ifHCOutUcastPkts = "1.3.6.1.2.1.31.1.1.1.11" + ifHCOutNUcastPkts = "1.3.6.1.2.1.31.1.1.1.12"
or (32bit counters):
ifInUcastPkts = "1.3.6.1.2.1.2.2.1.11" + ifInNUcastPkts = "1.3.6.1.2.1.2.2.1.12"
ifOutUcastPkts = "1.3.6.1.2.1.2.2.1.17" + ifOutNUcastPkts = "1.3.6.1.2.1.2.2.1.18"
Notice the calculation uses packets.
Now here comes the issue. Cisco switches 3650 / 3850 / 9000 series has the following bug:
CSCuw50024 : Bug Search Tool (cisco.com)
"Symptom: Output of 'show interfaces' provides counter of 'total output drops' in bytes not in packets. Corresponding SNMP polling for a given interface will also provide 'total output drops' in bytes not in packets."
Because the switches was sending the discards in bytes and not packets it meant the number was incorrect.
There is no feature on Solarwinds to change how the calculation is done so instead you have to run 'qos queue-stats-frame-count' on the switches (no impact to service).
Once I did that the discard rate was showing correctly, yay! 
Hope that helps someone!
