Failed to identify changed data on volume "xxxxxxxxx" will be performed as a full backup.

English Backup and data protection
1

Hi,

HDP pc agent version 1.4

HDP for PC/VM Version 2.3.3 (17/03/2026)

The system backuped id Win11 Pro

I make backup every 2 days , and it’s unable to make a partial backup (incremental)

The log msg is :

Failed to identify changed data on volume “xxxxxxxxx” will be performed as a full backup.

Before HDP pc agent upgrade in V1.4, incrementals run fine !

Is somebody has an idea ?

Thanks a lot in advance

Patrick

2

Please feel free to open a support ticket, or you can follow the steps here to extract the logs and send them to me via private message. Thanks!

How to extract the Hyper Data Protector debug logs to send for analysis? | QNAP

3

Hello Steve,

Many thanks to take in charge this issue.
I can’t attach aqll the files, but un EventLog/Application/VSS i’ve seen the following msgs:

[2026-02-05 11:37:08] [Information] (8224)
Le service VSS s’arrête, car le délai d’inactivité est dépassé.
It is in french but the acces un denied to do a querry
I guess the problem is here…

Account use to do backup is administrator on the NAS

Have you an idea how to correct this ?

Thanks a lot in advance
Patrick

[2026-02-05 12:06:58] [Error] (8194)
Erreur du service de cliché instantané des volumes : erreur lors de l’interrogation de l’interface IVssWriterCallback. hr = 0x80070005, Accès refusé.
. Cette erreur est souvent due à des paramètres de sécurité incorrects dans le processus du rédacteur ou du demandeur.

Opération :
Données du rédacteur en cours de collecte

Contexte :
ID de classe du rédacteur: {e8132975-6f93-4464-a53e-1050253ae220}
Nom du rédacteur: System Writer
ID d’instance du rédacteur: {f739b6a6-c2b3-4538-9565-7f7565e92139}

[2026-02-05 12:06:59] [Information] (8231)
informations Service VSS : création d’instantané lancée pour le jeu d’instantanés {9cbf2d36-3511-4cbd-9be9-c4d8a9799b49}.
Ligne de commande du processus : “C:\Program Files\QNAP\HDP\Bareos\Plugins\hdp\timeback\tools\timeback-plugin-service.exe”
Pile de l’appelant de processus :
Process[0] : timeback-plugin-service.exe
Process[1] : plugin-loader.exe
Process[2] : hdp-agent-service.exe

4

Hello
This issue has been resolved by this action:
In this REGEDIT key :
\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VSS\VssAccessControl
The value has been changed (REG_SZ) 0 → 1

This action give rights to query VSS and get changes to backup

That all