Reducing Excessive vSAN CnsSync Warnings

Products

• VMware vCenter Server

Issue/Introduction

Customers may experience excessive Info-level logging from VMware vSAN, specifically warnings related to datastore synchronization (CnsSync). The errors indicate that datastores cannot be synchronized due to missing or incomplete records, resulting in thousands of similar log entries per hour.

Environment

vSphere 7.x 

vSphere 8.x

Cause

The frequent occurrence of CnsSync warnings is caused by the vSAN component's default setting for the CNS (Content Storage Node) synchronization interval. By default, this interval is set to 1 minute, leading to a high volume of Info-level logs that are generated every time the synchronization process attempts to sync datastores.

Resolution

To reduce the frequency of these CnsSync warnings, follow these steps:

 

1. Locate VsanVcMgmtConfig.xml File :

   • Identify the path to the VsanVcMgmtConfig.xml file on your vSAN management node. This file is typically located in /etc/vmware/vsan/config/.

2. Modify newSyncInterval Parameter :

   • Open the VsanVcMgmtConfig.xml file using a text editor.
   • Locate the <property name="newSyncInterval">60</property> entry.
   • Change the value of 60 to a very large number (e.g., 2,147,483,647 seconds). This effectively disables frequent synchronization intervals and reduces log volume.

3. Save and Restart Services :

   • Save the changes to the VsanVcMgmtConfig.xml file.
   • Restart the vSAN management services for the changes to take effect. Typically, this involves restarting the vsan-healthd, vsan-vc, and vsan-cluster-managementd services.

Additional Information

• The CnsSync log entries are expected once after a restart of the system or when there is a change in the environment that triggers synchronization.
• Setting the synchronization interval to an extremely large value does not impact vSAN functionality, as it only affects the frequency of the logging process. This adjustment reduces unnecessary log volume without affecting data consistency.

 

By following these steps, customers can effectively reduce the occurrence of CnsSync warnings and manage their logging thresholds more efficiently.