Veeam 12 Upgrade Failed – Root Cause Analysis and How the Issue Was Finally Resolved

Recently, due to security vulnerabilities, I was performing an upgrade to Veeam Backup & Replication version 12.3. Today, upgrading one Veeam instance failed. This article documents the analysis process and the solution.

Problem Analysis

According to the prompt, checking the log (SetupBackupCheckerBR_26_10_2025_20_50_44.log) shows the error content:

ERROR [PGSQL] 28000: SSPI authentication failed for user "postgres" (Npgsql.PostgresException)

From the error message, it can be seen that error code 28000 indicates authentication failure, and SSPI (Security Support Provider Interface) is an authentication mechanism used by Windows. This error is a PostgreSQL database authentication failure. Some possible causes for the error are:

• Windows user mismatch
• pg_hba.conf configuration issue
• Service account permission issues

I suspected it was due to a Windows user mismatch because I was logged in with my own domain account, while the account that installed this VBR was a different one. Since there was no authorization, it couldn't connect to the PostgreSQL instance.

So I checked the Veeam official explanation:

This error occurs when the account used to interact with the PostgreSQL instance is not authorized.

Sure enough, since my account wasn't authorized, it naturally couldn't perform the upgrade operation. The solution is quite simple: use the account that deployed the VBR installation to perform the upgrade operation.

Checking the C:\Program Files\PostgreSQL\15\data\pg_ident.conf configuration file:

This configuration file records the domain account used during the VBR installation. I didn't have the password for this account, and the colleague who owned it had already left the company, so it couldn't be used. In this case, the only option was to add a new domain account. You can refer to the following steps.

Solution

Check the Veeam PostgreSQL log (C:\Program Files\PostgreSQL\15\data\log), scroll to the end where the error occurred:

Add the above domain account to the C:\Program Files\PostgreSQL\15\data\pg_ident.conf configuration file:

Save the file, then re-run the upgrade operation:

Problem solved, upgrade completed.

If the hostname of the VBR host has been changed, you might also encounter this issue and need to update the pg_ident.conf file.

Note: Starting from Veeam 12, the underlying data storage can use a PostgreSQL database.

Why Veeam 12 Upgrade Failures Are Often Misleading

Many administrators assume a Veeam 12 upgrade failure is caused by installer bugs or corrupted packages. In reality, upgrade errors are frequently triggered by environmental issues such as:

• Insufficient disk space on system or configuration volumes

• Leftover services or locked processes

• Repository metadata inconsistencies

• Unsupported OS or missing prerequisites

These hidden problems often surface only during the upgrade process, making root cause analysis critical.

Key Lessons Learned from This Veeam 12 Upgrade Case

This case highlights several important upgrade best practices:

• Always validate disk space and file system health before upgrading

• Stop all Veeam-related services cleanly

• Check Windows Event Viewer and Veeam logs, not just installer messages

• Do not ignore “non-critical” warnings shown during pre-checks

Veeam upgrades are reliable—but only when the environment is clean.

✅ Recommended Pre-Upgrade Checklist for Veeam 12

Before upgrading Veeam Backup & Replication, ensure:

• Backup repositories are online and healthy

• No active backup or replication jobs are running

• Windows updates are completed

• Antivirus exclusions are configured for Veeam directories

• A configuration backup has been taken

📌 External reference (Veeam official upgrade guide):
https://helpcenter.veeam.com/docs/backup/vsphere/upgrade_vbr.html