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Azure Backup Server DPM is unable to enumerate contents in \\?\Volume error

Richard Hendrix 5 Reputation points
2024-12-17T15:30:45.53+00:00

I'm running the latest version of Microsoft Azure Backup Server (DPM), 14.0.46.0 and I'm trying to update (refresh) the data sources on a 2022 Hyper-V server. The Hyper-V server has been connected to the MABS server and successfully backing up VMs for about 6 months now. I've added some new VMs and I need to refresh so they show in the list and I can add them for backup. However, I get the following message when I click Refresh on this host.

DPM is unable to enumerate contents in \?\Volume{4e629d68-c0cb-49dc-9718-dfb2086dd544}\ on the protected computer <hyper-v host name>. Recycle Bin, System Volume Information folder, non-NTFS volumes, DFS links, CDs, Quorum Disk (for cluster) and other removable media cannot be protected. (ID: 38)

I searched on the host and found a volume called 4e629d68-c0cb-49dc-9718-dfb2086dd544 in the registry with no mount points (according to the mountvol command). After backing up the registry, I removed the 2 entries related to volume 4e629d68-c0cb-49dc-9718-dfb2086dd544 but the MABS server still shows the error with the same volume.

I've tried

  • stopping/starting the DPMRA Service on the host
  • completely uninstalled the agent on the host
  • searched the registry on the MABS server for volume 4e629d68-c0cb-49dc-9718-dfb2086dd544 (nothing)
  • Searched the PSDataSourceConfig.xml file for the volume (not there, never was)

I have two other hosts, 2016 OS/Hyper-V, and they refresh fine. All three have the firewalls OFF (for testing).

I'm at a loss as to where MABS is still pulling this volume from and how to get rid of it so I can refresh and back up my new VMs.

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  1. Richard Hendrix 5 Reputation points
    2024-12-17T19:56:57.5+00:00

    So after restarting the Hyper-V host, the volume reappeared in the mountvol command results. So I found a command to map a drive letter to the volume (turns out it's the EFI volume).

    mountvol k: \?\Volume{4e629d68-c0cb-49dc-9718-dfb2086dd544}\

    Once I did that, the Refresh didn't error. The VMs didn't immediately show up, but I checked about 10 minutes later and the new VMs had populated in the listing for the host.

    Not sure why mounting the volume with a drive letter fixed the issue, but just glad it's working now.

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  2. AlexZhu-MSFT 6,036 Reputation points Microsoft Vendor
    2024-12-18T07:27:33.3966667+00:00

    Hi Richard,

    Thank you very much for the valuable input and people with similar situations may benefit from the working solution. Here's a short summary:

    Products Involved:

    ===================

    Microsoft Azure Backup Server (DPM), 14.0.46.0

    2022 Hyper-V server

    Problem Description:

    ===================

    trying to update (refresh) the data sources on a 2022 Hyper-V server connected to the MABS server, get the following message:

    DPM is unable to enumerate contents in ?\Volume{4e629d68-c0cb-49dc-9718-dfb2086dd544}\ on the protected computer <hyper-v host name>

    Solutions:

    ===================

    mounting the volume with a drive letter fixed the issue, the command is as below:

    mountvol k: ?\Volume{4e629d68-c0cb-49dc-9718-dfb2086dd544}\

    Regards,

    Alex Zhu

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