Only one uplink is being utilized for vSAN traffic while using Route Based on Physical NIC Load with an Active/Active vmnic Configuration.
Article ID: 394368
Updated On:
Products
Issue/Introduction
When using Dedicated vmnics for vSAN traffic in a Active/Active configuration and using "Route Based on Physical NIC Load" only one vmnic is active at any one time for vSAN traffic.
Environment
Vmware vSAN(all versions)
Cause
Per the following document we see that "Route Based Physical NIC Load" will move the VMKport to a new vmnic when that vmnic is under contention by multiple services but as these vmnics are dedicated to vSAN only, load will not be moved as there is no other contention on the vmnics. This policy will not load balance vSAN traffic across multiple vmnics at the same time.
Route Based on Physical NIC Load
We see how Route Based on Physical NIC Load works below
Route Based on Physical NIC Load is based on Route Based on Originating Virtual Port, where the virtual switch monitors the actual load of the uplinks and takes steps to reduce load on overloaded uplinks. This load-balancing method is available only with a vSphere Distributed Switch, not on vSphere Standard Switches.
The distributed switch calculates uplinks for each VMkernel port by using the port ID and the number of uplinks in the NIC team. The distributed switch checks the uplinks every 30 seconds, and if the load exceeds 75 percent, the port ID of the VMkernel port with the highest I/O is moved to a different uplink.
Pros
No physical switch configuration is required.
Although vSAN has one VMkernel port, the same uplinks can be shared by other VMkernel ports or network services. vSAN can benefit by using different uplinks from other contending services, such as vMotion or management.
Cons
As vSAN typically only has one VMkernel port configured, its effectiveness is limited.
The ESXi VMkernel reevaluates the traffic load after each time interval, which can result in processing overhead.
Resolution
In order to utilize bandwidth across Multiple VMnics a more Advanced NIC Teaming configuration will need to be deployed.
Please review the following documents on the advanced Nic teaming and select an option that works for you.
Utilizing some sort of link aggregation such as LACP to gain additional bandwidth using multiple uplinks.
Feedback
