Dell VxRail Network Planning Guide

Enable flow control

Network instability or congestion contributes to low performance in VxRail, and has a negative effect on the vSAN I-O datastore operations. VxRail recommends enabling flow control on the switch to assure reliability on a congested network. Flow control is a switch feature that helps manage the rate of data transfer to avoid buffer overrun. During periods of high congestion and bandwidth consumption, the receiving network will inject pause frames for a period of time to the sender network to slow transmission in order to avoid buffer overrun. The absence of flow control on a congested network can result in increased error rates and force network bandwidth to be consumed for error recovery. The flow control settings can be adjusted depending on network conditions, but VxRail recommends that flow control is receive on and transmit off.