We are using Veeam Enterprise Backup & Replication 12 in a mixed VMware VM and physical Windows network.
We have upgraded all of our Windows servers to Server 2025. Backups on non-domain controllers had no issue post update but our domain controllers are all failing with the same error once the OS was upgraded: Failed to index guest file system. VSSControl: Index failed
There are no connectivity issues between the domain controllers and the Veeam servers and proxies. The domain controllers were not all upgraded on the same day, but each would fail as soon as the OS upgrade occurred. So one day the DC running on Server 2022 would be able to be backed up with no issues, the night its upgraded it would fail. No other changes other than OS upgraded. No changes to virtualization or network infrastructure.
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How much free space is on the servers experiencing this issue?
About 266GB free on each DC out of a 300GB system drive.
Hmm, that’s definitely not the issue then.
By the way, do you actually require guest-indexing enabled on this job? Are your domain controllers acting as file servers and you need the files indexed for browsing in Enterprise Manager? A common misconception is that guest indexing is required to enable file-level restores, but that is not the case.
I realize that doesn’t fix the error at hand, but disabling it would be a workaround.
Do you use gMSA accounts for guest indexing? Does the user acct used for indexing succeed? You can test it in the Job settings.
Do you actually require guest processing? I personally don’t use it and haven’t for over 10yrs cuz of this very reason...account failure issues. Am in agreement with Tommy here on that.
Can you see any more detail in the backup job logs? C:\ProgramData\Veeam\Backup\<job-name-log>
At the very least, you may need to reach out to Veeam Support to further assist. I’m not seeing anything else here or on the Forums at the moment...will continue to look. But again, Support may be your best bet here to suggest something we’ve overlooked.
Best.
Do you actually require guest processing? I personally don’t use it and haven’t for over 10yrs cuz of this very reason...account failure issues. Am in agreement with Tommy here on that.
Important to distinguish guest processing(Application-Aware processing) vs guest indexing. As these are domain controllers it is likely important to leave Application-Aware processing enabled.
However I’m pretty sure Guest Indexing is not needed.
Also @CPI ...check and see if the VSS Service is running on your DCs. If not, go into your Event Viewer and check if anything is shown there on why it may not be able to.
I did find another couple posts with the same error, but it was space-related:
Lastly, I saw this post on some troubleshooting steps to try:
@Tommy O'Shea - well, I use Guest Processing interchangeably to mean both because they fall under that named section of the Job wizard.
Guest Processing
But agree...to mitigate confusion is probably best to be specific.
Hi Guys, thanks for the replies. We had the DCs in the same backup jobs as non DCs and we had Guest Processing on for all of them. Honestly, we could more than likely disable it across the board (leave application). We no longer do any file hosting on any of the servers. Everything is either embedded into a DB or now on our NAS servers which have their own backup job. I have to leave in a bit for a doctors appointment. I will post the log contents when I get back.
@CPI - ok; and..to be clear...AAIP can be enabled, but you really don’t need guest indexing enabled. If you disable that and run the job..see if it then is successful.
@CPI, sounds good. It’s fine to leave them in the same job. You can specify in the Guest Processing tab which machines you want to have their applications processed by clicking “Applications...” button.
First thing I usually do is set them all to “Try application processing, but ignore failures". This will cause backups where AA failed to still capture a vm-level backup, and not fail outright. (It will show a warning instead)
For the ones you don’t need AA for, you can disable processing completely.
@CPI - ok; and..to be clear...AAIP can be enabled, but you really don’t need guest indexing enabled. If you disable that and run the job..see if it then is successful.
Yeah I created a new backup job for just the DC’s and enabled Application Aware Processing but not Guest Processing. I kicked off the job when the wizard ended and it successfully completed the backup within a few minutes. Would still like to know why this occurred only after a OS upgrade on DCs and no other servers but not something critical to know.
@CPI, sound good. It’s fine to leave them in the same job. You can specify in the Guest Processing tab which machines you want to have their applications processed by clicking “Applications...” button.
First thing I usually do is set them all to “Try application processing, but ignore failures". This will cause backups where AA failed to still capture a vm-level backup, and not fail outright. (It will show a warning instead)
For the ones you don’t need AA for, you can disable processing completely.
I think I forgot about that. But it should be fine as its own job for now.
@CPI - honestly...indexing in Veeam is a fickle thing imo
Was this issue resolved in update 12.3.2?
12.3.2.3617
Resolved Issues
Application Item Recovery
Veeam Explorer for Active Directory: Unable to connect to a target domain controller when SSL is enabled.
@tylercourtney - maybe; that resolution item doesn’t specifically state for Win2025. But, worth a try to look at after upgrading (recommended to upgrade due to a severe critical patch in the upgrade ISO)
