Dell VxRail Network Planning Guide

Enable flow control

Network instability or congestion can negatively affect VxRail and vSAN data store performance. Do not enable traditional Ethernet flow control (pause frames) in modern 10 GbE or higher environments.

Pause frames can cause head-of-line (HOL) blocking, where congestion on one traffic stream pauses all other streams on the same link. This may degrade performance instead of improving it.

Modern NICs and switches provide sufficient buffering and congestion management mechanisms such as ECN, PFC for storage-specific networks, and QoS to handle transient congestion without requiring global pause frames.

For flow control, the following apply::

• Disable Ethernet flow control (both transit and receive) on all 10 GbE and faster interfaces.
• For environments that require lossless traffic, such as RoCE or FCoE: use PFC, IEEE 802.1Qbb instead of global pause frames.
• On 1 GbE interfaces, consider flow control if you expect legacy storage traffic or congestion. This is not typical for modern VxRail deployments.