NSX-T Backup Failure: UI Timestamp Continually Updates Every 5 Minutes When SFTP Target Unreachable

Products

• VMware NSX

Issue/Introduction

When a scheduled NSX-T Data Center backup fails due to an unreachable or unavailable SFTP target, the NSX Manager UI initially displays the Node backup status as "Failed" with an accurate timestamp of the initial failure. However, the timestamp associated with the Cluster backup job in the UI continues to update approximately every 5 minutes, even though the backup is not succeeding and the SFTP target remains offline.

This behavior has been specifically observed after NSX-T  version 4.2.2.1

Environment

VMware NSX  4.x

Cause

This behavior is by design and indicates NSX-T Data Center's built-in backup retry mechanism.

• When a backup attempt fails (e.g., due to an unreachable SFTP server, network connectivity issues, or insufficient disk space on the target), NSX-T does not immediately cease the operation.
• Instead, it initiates retries at regular intervals, typically every 5 minutes, ( or user defined intervals )  to account for transient issues such as temporary network glitches or momentary unavailability of the SFTP server.
• The NSX-T UI reflects the timestamp of the latest backup attempt, regardless of whether that attempt was successful or failed. Therefore, even if the SFTP target remains offline and each retry also fails, the UI will continue to update the "last attempt" timestamp with each subsequent retry.
• Changes introduced in NSX-T  later versions in the 4.x.x series may have refined this retry interval or the UI's reporting logic, making this specific behavior more apparent.

Resolution

This continuous updating of the timestamp for a failed backup is an expected behavior and not an indication of a new or escalating issue within NSX-T Data Center itself. It serves to show that the NSX Manager is still actively attempting to complete the backup.

To resolve the underlying backup failure and stop the continuous timestamp updates:

1. Address the Root Cause: Ensure the configured SFTP backup target is:
   • Operational and running.
   • Network accessible from all NSX Manager nodes.
   • Has sufficient free disk space to accommodate the backup files.
   • Has correct credentials configured in NSX-T.
2. Resume Backup Schedule: Once the SFTP target is verified and accessible, NSX-T should be able to successfully complete the next scheduled backup, and the UI status will then reflect "Success" with the new timestamp.
3. Alternatively (for troubleshooting): If the SFTP server cannot be brought online immediately, consider temporarily disabling the scheduled backup within NSX-T until the target is ready.

Note : The Fix is available After 9.0.1 GA, mostly at the end of September 2025

Additional Information

• Verification: To confirm this behavior and understand the failure details, review the NSX Manager logs. Look for entries in vsm.log or proton-backup-restore.log that indicate repeated backup attempts and associated failure messages (e.g., "SFTP connection failed," "target unreachable") at approximately 5-minute intervals.
• Impact: While the UI continuously updates the timestamp, it accurately reflects that the backup is not completing successfully. No successful backup archives are being stored during this period. It is critical to address the underlying SFTP issue to ensure data recoverability.
• Best Practice: Implement proactive monitoring of your NSX-T backup status and SFTP target availability to catch and resolve issues promptly.