Receive Side Scaling allows multiple cores on the receive side for processing incoming traffic.

Without RSS, receiving ESXi hosts only use one physical queue and hence one lcore for packet processing. When the receive side data increases it creates a bottleneck at the single core. The overall throughput performance might decrease. With RSS enabled on the NIC, you can configure multiple hardware queues to process requests from VMs. Before you use a NIC card to leverage the RSS functionality, use the VMware Compatibility Guide for I/O to confirm whether the NIC card driver supports RSS. Most of the NIC cards support at least 4 queues. So, RSS might provide 4x throughput performance improvements.

Receive Side Scaling allowing multiple cores on a ESXi host to process traffic.

You can choose to configure RSS in these modes:
  • enable Default Queue Receive Side Scaling (DRSS)
  • enable RSS engine dedicated to a single vNIC queue
  • enable RSS engine shared by multiple vNIC queues