Repository fails to mount. Failed to open the MBR file. (4044976)

• Failed to open the MBR file - Access is denied (0x80131500)
• File system is incomplete 'DvmFSIncomplete'
• The folder with repository RepositoryName is empty.
• A repository check fails with DVMFSIO.

The Rapid Recovery Core is not able to open a metadata file because:

• It is Corrupted.
• Is been used by a third party software like an antivirus.
• The NT\SYSTEM account does not have permission.
• Was deleted or renamed.
• The volume is full.

Disclaimer: Please follow all steps as described; otherwise, the data on the repository could be lost. If preferred, please contact Quest support for assistance completing the instructions.

Workaround#1 - Verify that NT\SYSTEM has full control

1. Open 'File Explorer' and navigate to the repository metadata path
2. Locate the dfs.mbr file
3. Right Click in the file and select "Properties"
4. Verify that NT\SYSTEM has 'Full control'

Workaround#2 - Add antivirus exclusions

Follow article to add exclusions to Antivirus and Security software to avoid lock issues.

Workaround#3 - Reboot the Rapid Recovery Core server.

Restarting the server should allow the file to be released from the lock.

Workaround#4 - Recreate the dfs.mbr file

1. How To Stop or restart the Core Service and wait for the process to end.
2. Open 'File Explorer' and navigate to the repository metadata path.
3. Rename the "dfs.mbr" file to "dfs.mbr.old".
4. Create a blank txt file with name "dfs.mbr".
5. Remove the .txt extension from the "dfs.mbr" file.
6. Start the RapidRecovery Core service.

Workaround#5 - Ensure Sufficient Free Space on the Repository Volume

To avoid repository mount failures and ensure stable operation, always maintain adequate free space on the storage volume hosting the Rapid Recovery repository. When a volume becomes full, it may block new writes, restrict access, or trigger protocol-level errors (especially over SMB). Additionally, storage systems—whether NAS, direct-attached, or iSCSI—may enforce quotas or space limits that can prevent further data operations even if the volume appears to have free space.

Maintaining free space helps:

• Prevent write failures and file access issues.
• Avoid SMB/NFS errors that mimic file locking.
• Ensure that snapshot, quota, or storage policy limits do not interfere with repository access.

Workaround#6 - Verify Storage Health

1. Ensure the storage is healthy: Storage systems may appear healthy but still have underlying issues, such as impending failures, block issues, or a RAID puncture.

2. Copy or move repository folders to another storage location:

   • If storage issues are affecting repository metadata files, they will fail to copy, indicating a problem.

   • Ensure you have a backup before proceeding further.

3. Run CHKDSK /r:

   • This command repairs block-level issues.

   • Warning: Before running CHKDSK /r, copy or move the repository folders, as the command can cause corruption. Refer to the article Running CHKDSK Repair on a Disk That Contains an Archive or Repository Volume May Result in Data Loss for details.

For further assistance, contact Quest Support.