High percentage at "pNIC vSwitch Port Drop Rate" in VSAN Performance stats under Physical Adapter tab when there is no traffic on that vmnic
Article ID: 408796
Updated On:
Products
Issue/Introduction
- High number of percentage drops detected at "pNIC vSwitch Port Drop Rate" on the vmnic that is very little or not utilized by vmk or VM network traffic, like in the following screenshot:
- When there is significant traffic seen in Monitoring > VSAN > Performance > Physical Adapter > "pNIC Packets Per Second" counter on the vmnic in question, the drops rate is practically at 0%
Environment
VMware vSAN 8.x
Cause
-
"pNIC vSwitch Port Drop Rate" checks the vSwitch stats, which can include valid drops, for example if the physical switch sends a packet that can't be delivered (such as multicast or unknown unicast). If a vmnic is not being utilized, the drop percentage calculated from all traffic being forwarded to the vmnic may appear high.
-
When the vmnic is being utilized and more traffic is being received, the percentage "pNIC vSwitch Port Drop Rate" would drop near 0% even if the same number of packet drops are still occurring.
Resolution
This is an expected behavior if there is no VM/vmk traffic on the vmnic in question.
Additional Information
As per vSAN Performance Graphs in the vSphere Web Client Part 1 :
pNIC vSwitch Port Drop Rate
This graph shows percentage of Physical NIC vSwitch Port Drop Rate.
| Metrics | Metrics Description | Metric ID in API | Corresponding Entity Type | Corresponding Real-time Entity type |
|---|---|---|---|---|
| Inbound Packet Drop Rate of pNic vSwitch Port | Percentage of Physical NIC Inbound vSwitch Port Drop Rate. | portRxDrops | vsan-pnic-net | hr-vsan-pnic-net |
| Outbound Packet Drop Rate of pNic vSwitch Port | Percentage of Physical NIC Outbound vSwitch Port Drop Rate. | portTxDrops | vsan-pnic-net | hr-vsan-pnic-net |
Q: Would setting the uplinks for the vSAN vmkernel adapter to Active/Standby help mitigate this alert?
A: Keeping the uplink in an Active/Standby or Active/Active configuration makes no difference. This is because the pNic error health check monitors all the uplinks configured for the vSAN vmkernel's port group.
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