Diagnosing and Resolving vMotion Performance Issues in 1 Gbps Network Environments
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Diagnosing and Resolving vMotion Performance Issues in 1 Gbps Network Environments

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Article ID: 375717

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Updated On:

Products

VMware vSphere ESXi

Issue/Introduction

Users may experience severe network performance degradation and connectivity loss events during vMotion tasks in environments using 1 Gbps network interfaces. This article provides guidance on diagnosing throughput issues and offers resolution steps for improving vMotion performance.

Environment

- VMware vSphere 7.0 or later
- ESXi hosts with 1 Gbps network interfaces
- vSphere Distributed Switch (VDS)
- Virtual machines with 1 GB or more memory

Cause

vMotion operations can saturate 1 Gbps network links, especially when multiple concurrent vMotions occur. This saturation can lead to network-wide performance issues and connectivity problems for other services.

Resolution

  1. Diagnose throughput issues:
    1. SSH into the ESXi host and use the following command to monitor vMotion network traffic: 
      • esxtop -n
    2. Press 'n' to switch to the network view.
    3. Look for the vmknic associated with vMotion (usually vmk1) and observe the MbTx/s (Megabits transmitted per second) column during a vMotion operation.
    4. Calculate the average throughput over the duration of the vMotion:
      • Average Throughput (Mbps) = (VM Memory Size in MB * 8) / vMotion Duration in Seconds

  2. If the average throughput approaches or exceeds 800 Mbps on a 1 Gbps link, consider the following steps:
    1. Upgrade network interfaces to 10 Gbps or higher.
    2. Configure a dedicated vMotion network stack: 
      • esxcli network ip interface tag remove -i vmk1 -t VMotion
      • esxcli network ip interface set -i vmk1 -s vmotion
      • esxcli network ip interface tag add -i vmk1 -t VMotion
    3. Separate vMotion traffic onto its own VLAN.
    4. Implement vMotion scheduling and throttling:
      • In the vSphere Client, go to Host > Configure > System > Advanced System Settings
      • Set Migrate.NetTimeout to a higher value (e.g., 300 seconds)
      • Set Migrate.NetRetries to a lower value (e.g., 10)
    5. Optimize vSphere Distributed Switch (VDS) configuration:
      • Enable Network I/O Control (NIOC)
      • Configure load balancing policy to "Route based on physical NIC load"
      • Implement traffic shaping policies for vMotion traffic

  3. Verify the changes:
    1. Perform a test vMotion and monitor the network throughput using the esxtop command.
    2. Confirm that other network services are not impacted during vMotion operations.

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