Unable to backup with MARS agent due to error

Question

Unable to backup with MARS agent due to error

Diana Piloya 185

I am getting this error and looking to find a solution: Error message

The current backup operation failed because the number of data transfer failures was more than 1000 Specified files could not be processed.

I moved scratch folder from C:\ drive to E:\ drive, ran a full disk scan but this error still unable to clear this error. How can I resolve this.

User's image

Suchitra Suregaunkar 9,270 Reputation points Microsoft External Staff Moderator

2026-02-26T03:45:36.54+00:00

Hello Diana Piloya

Thank You for posting your query on Microsoft Q&A platform.

We are looking into your issue and will keep you posted updates.

Thanks,
Suchitra.
Suchitra Suregaunkar 9,270 Reputation points Microsoft External Staff Moderator

2026-02-26T04:17:10.1833333+00:00
Hello Diana Piloya

This error occurs when the Azure Recovery Services (MARS) agent encounters more than 1000 file‑level read or transfer failures during a backup job. Once this threshold is reached, the MARS agent intentionally stops the backup job.

This error is caused by repeated file‑level failures on the protected server, such as:

Corrupt, locked, or inaccessible files/folders (for example, application temp files, cache folders, or files held open by running services)

Antivirus or security software blocking file reads during backup

Unsupported files or file attributes

Backup retry running in unoptimized mode after a previous failure, causing the agent to scan the entire volume and quickly exceed the failure threshold

Moving the scratch folder or running a disk scan alone does not resolve the issue if the underlying file‑level failures persist.

To resolve this issue, follow only the steps below, which are officially supported:

Identify the failing files

Review MARS agent logs under: C:\Program Files\Microsoft Azure Recovery Services Agent\Temp

Look for repeated file access or read errors.

Exclude problematic files or folders

Exclude corrupt, locked, or application‑specific folders (such as temp, cache, or working directories) from the backup selection.

Excluding unsupported or inaccessible files is a documented requirement.

Configure antivirus exclusions

Exclude the Azure Backup agent binaries, installation directories, and the configured scratch folder from real‑time antivirus scanning.

Antivirus interference is a cause of MARS backup failures.

Run a manual backup

After exclusions are applied, run a manual backup.

Once a successful backup completes, subsequent scheduled backups stabilize and no longer hit the 1000‑failure threshold.

Troubleshoot Azure Backup (MARS) agent https://learn.microsoft.com/azure/backup/backup-azure-mars-troubleshoot

Antivirus exclusion and MARS best practices https://learn.microsoft.com/azure/backup/backup-azure-mabs-troubleshoot

This issue is not caused by the Recovery Services vault or Azure service side. It is triggered locally on the protected server when file‑level read failures exceed the supported threshold.

Thanks,
Suchitra.
Diana Piloya 185 Reputation points

2026-02-26T12:25:49.3366667+00:00

thank you @Suchitra , I did all this, run an on demand backp but now get this error. how can i proceed
Diana Piloya 185 Reputation points

2026-03-02T05:46:22.43+00:00

Hello @Suchitra Suregaunkar , Any feedback from the above?
Suchitra Suregaunkar 9,270 Reputation points Microsoft External Staff Moderator

2026-03-02T18:54:11.2366667+00:00
Hello @Diana Piloya

This message indicates that the MARS agent failed during the data transfer phase after backup processing had already started. This is a local agent‑side failure, typically caused by interruption or instability during transfer, not by the Recovery Services vault itself.

Please follow only the steps below:

Discard the failed recovery point and retry

When this message appears current recovery point is not usable and should be ignored. Run a new manual backup after completing the checks below.

Validate scratch location health and free space

Microsoft requires:

Scratch folder on a local NTFS disk

Minimum 5–10% free space

No disk or NTFS errors

Even if this was checked earlier, re‑validate before retrying. Scratch instability can trigger transfer‑phase failures.

Confirm antivirus exclusions (mandatory): Antivirus real‑time scanning can interrupt data transfer and cause this error.

Ensure exclusions exist for:

cbengine.exe

MARS installation directory

Scratch folder location

This is a required configuration, not optional.

Reference: https://docs.azure.cn/en-us/backup/backup-azure-mabs-troubleshoot

Check MARS agent logs for transfer failures

Review logs at:

C:\Program Files\Microsoft Azure Recovery Services Agent\Temp

Look specifically for:

Transfer interruptions

File read or stream failures

Sudden job termination during upload

Re‑register the server (if error repeats)

If the same error occurs again after a clean retry, it is recommended re‑registering the server to reset backup metadata.

Stop backups

Unregister the server from the vault

Re‑register using the original passphrase

Reconfigure backup policy

Run a manual backup

Thanks,
Suchitra.
Suchitra Suregaunkar 9,270 Reputation points Microsoft External Staff Moderator

2026-03-03T21:13:42.5+00:00

Hello @Diana Piloya

Kindly let us know if the solution provided worked for you.

If you found the comment helpful, please consider clicking "Upvote it".

If the resolution did not help, feel free to share more details about the challenge you’re still facing. Any additional information such as your current issue or specific errors will help us perform a deeper analysis and provide more targeted guidance.

We’re happy to continue assisting and work with you toward the right solution.

Thanks,

Suchitra.
Naveena Patlolla 8,520 Reputation points Microsoft External Staff Moderator

2026-03-09T13:57:04.8733333+00:00

Hello @Diana Piloya
Just want to check if the above solution worked for you or else please let us know if any help, we are always here to help whenever you need us.

Please do consider to “up-vote” whenever the information provided helps you, this can be beneficial to other community members.
Diana Piloya 185 Reputation points

2026-03-10T04:50:09.3+00:00

Hello @Naveena Patlolla I tried the above steps including re-registering the MARS agent though i am still getting the same error
Suchitra Suregaunkar 9,270 Reputation points Microsoft External Staff Moderator

2026-03-10T15:46:20.4733333+00:00
Hello @Diana Piloya

After further investigation we have an update that the backup has multiple errors : CBPReplicationFailed | MaxFailedFilesReachedInBackup.

The first backup failed MaxFailedFilesReachedInBackup because too many files could not be processed during the scan phase.

Failed: Hr: = [0x80070002] Failed to read local client stamp file - [C:\Program Files\Microsoft Azure Recovery Services Agent\Scratch\MicrosoftBackupProvider\SAL\ClientStamps{F5A802C7-7B4A-4A7B-ABDF-6F127E628E71}_3603495430324975007_3603421437448520489]

After that was cleared, the next backup progressed further, started uploading data, but then failed during replication due to an upload‑level interruption or file‑read issue with the error CBPReplicationFailed, because the Azure Backup agent encountered corrupted files under ProgramData\Kaspersky Lab during the data upload phase:

For example :

"PreciseTimeStamp": 2026-03-05T07:38:45.7829731Z, "Message": Failed: Hr: = [0x8000ffff] [DebugTransferStuck] SetNextBuffer() failed on file \\?\Volume{619c004e-0000-0000-0000-602200000000}\ProgramData\Kaspersky Lab\KES.21.21\Patches\kes11\kes11_22\aes256\en\bases\updates\umids\i386\win\umids.kdcpv:00000218CAAF0210, cb:196608, pcbRead:0, "TaskId": 6059481e-6c9e-453b-9355-2f9b38b21d13, "FileNameLineNumber": MtfFile.cpp(565), "ServiceName": tel, "Level": WARNING

Basically the backup failed because a specific Kaspersky files are corrupted at the file‑system level:

Error while reading file. Data is present, but are out of extents.

ChkDsk may help.

Try deleting and recreating file.

Assertion Failure :: false SetNextBuffer() failed

And the same files repeat:

\ProgramData\Kaspersky Lab\KES.21.21\Patches...\umids.kdcpv

\ProgramData\Kaspersky Lab\KES.21.21\Patches...\umids.kdc

\ProgramData\Kaspersky Lab\KES.21.21\Patches...\umids.kdl

The full error: 3/5/2026, 7:38:45.7827175 AM skipping stream and continuing backup 6059481e-6c9e-453b-9355-2f9b38b21d13 MtfFile.cpp(582) tel NORMAL 3/5/2026, 7:38:45.7826552 AM Failed: Hr: = [0x8000ffff] [DebugTransferStuck] SetNextBuffer() failed on file \\?\Volume{619c004e-0000-0000-0000-602200000000}\ProgramData\Kaspersky Lab\KES.21.21\Patches\kes11\kes11_22\aes256\en\bases\updates\umids\i386\win\umids.kdcpv:00000218CB7F1F30, cb:196608, pcbRead:0 6059481e-6c9e-453b-9355-2f9b38b21d13 MtfFile.cpp(565) tel WARNING 3/5/2026, 7:38:45.7825914 AM Failed: Hr: = [0x00000000] CDataVhdWriter::SetNextBuffer Flush buffer queue failed for file \\?\Volume{9c47b02b-4edc-4bf5-b560-d5d3962dd4fe}\ProgramData\Kaspersky Lab\KES.21.21\Patches\kes11\kes11_22\aes256\en\bases\updates\umids\i386\win\umids.kdc 6059481e-6c9e-453b-9355-2f9b38b21d13 DataVhdWriter.cpp(645) tel WARNING 3/5/2026, 7:38:45.7825272 AM Error while reading file. Data is present, but are out of extents. ChkDsk may help. Try deleting and recreating file. Extent Information: File offset 0 | Volume offset 0 | Extent size = 0 6059481e-6c9e-453b-9355-2f9b38b21d13 DataVhdWriter.cpp(481) tel WARNING

Root Cause of the Issue:

Files under the path ProgramData\Kaspersky Lab are corrupted.

the logs above show repeated read and assertion failures (“data is present, but out of extents”) on these files.

When the agent encountered these files during replication it was not able to continue transferring data which explain the CBPReplicationFailed error.

Recommendations: the failure caused by a corrupted files under : C:\ProgramData\Kaspersky Lab\

Try the below resolution steps:

1. Clean or regenerate the affected Kaspersky files.

To recreate, copy the file to the different location

Delete original file

Move copied file to original location.

Retry the backup operation.

2. Exclude the problematic file: As these files are antiviruses update/cashe data and do not provide restore value and this is the recommended approach.

Thanks,
Suchitra.
Diana Piloya 185 Reputation points

2026-03-12T02:13:03.44+00:00

Hello @Suchitra Suregaunkar , I carried out all these steps though I keep getting the same error. How can i get a successful backup?
Diana Piloya 185 Reputation points

2026-03-12T02:32:41.62+00:00

Hello @Suchitra Suregaunkar , I have tried the recommended approach and excluded the suggested files though I am still getting this error.
Suchitra Suregaunkar 9,270 Reputation points Microsoft External Staff Moderator

2026-03-12T18:14:10+00:00

Hello @Diana Piloya

Thanks for the update, we will look into it and will keep you posted further updates.

1 answer

Your answer

Suchitra Suregaunkar 9,270 Reputation points Microsoft External Staff Moderator

2026-02-26T03:45:36.54+00:00

Hello Diana Piloya

Thank You for posting your query on Microsoft Q&A platform.

We are looking into your issue and will keep you posted updates.

Thanks,
Suchitra.
Diana Piloya 185 Reputation points

2026-02-26T12:25:49.3366667+00:00

thank you @Suchitra , I did all this, run an on demand backp but now get this error. how can i proceed
Diana Piloya 185 Reputation points

2026-03-02T05:46:22.43+00:00

Hello @Suchitra Suregaunkar , Any feedback from the above?
Suchitra Suregaunkar 9,270 Reputation points Microsoft External Staff Moderator

2026-03-02T18:54:11.2366667+00:00

Hello @Diana Piloya

This message indicates that the MARS agent failed during the data transfer phase after backup processing had already started. This is a local agent‑side failure, typically caused by interruption or instability during transfer, not by the Recovery Services vault itself.

Please follow only the steps below:

Discard the failed recovery point and retry

When this message appears current recovery point is not usable and should be ignored. Run a new manual backup after completing the checks below.

Validate scratch location health and free space

Microsoft requires:

Scratch folder on a local NTFS disk

Minimum 5–10% free space

No disk or NTFS errors

Even if this was checked earlier, re‑validate before retrying. Scratch instability can trigger transfer‑phase failures.

Confirm antivirus exclusions (mandatory): Antivirus real‑time scanning can interrupt data transfer and cause this error.

Ensure exclusions exist for:

cbengine.exe

MARS installation directory

Scratch folder location

This is a required configuration, not optional.

Reference: https://docs.azure.cn/en-us/backup/backup-azure-mabs-troubleshoot

Check MARS agent logs for transfer failures

Review logs at:

C:\Program Files\Microsoft Azure Recovery Services Agent\Temp

Look specifically for:

Transfer interruptions

File read or stream failures

Sudden job termination during upload

Re‑register the server (if error repeats)

If the same error occurs again after a clean retry, it is recommended re‑registering the server to reset backup metadata.

Stop backups

Unregister the server from the vault

Re‑register using the original passphrase

Reconfigure backup policy

Run a manual backup

Thanks,
Suchitra.
Suchitra Suregaunkar 9,270 Reputation points Microsoft External Staff Moderator

2026-03-03T21:13:42.5+00:00

Hello @Diana Piloya

Kindly let us know if the solution provided worked for you.

If you found the comment helpful, please consider clicking "Upvote it".

If the resolution did not help, feel free to share more details about the challenge you’re still facing. Any additional information such as your current issue or specific errors will help us perform a deeper analysis and provide more targeted guidance.

We’re happy to continue assisting and work with you toward the right solution.

Thanks,

Suchitra.
Naveena Patlolla 8,520 Reputation points Microsoft External Staff Moderator

2026-03-09T13:57:04.8733333+00:00

Hello @Diana Piloya
Just want to check if the above solution worked for you or else please let us know if any help, we are always here to help whenever you need us.

Please do consider to “up-vote” whenever the information provided helps you, this can be beneficial to other community members.
Diana Piloya 185 Reputation points

2026-03-10T04:50:09.3+00:00

Hello @Naveena Patlolla I tried the above steps including re-registering the MARS agent though i am still getting the same error
Diana Piloya 185 Reputation points

2026-03-12T02:13:03.44+00:00

Hello @Suchitra Suregaunkar , I carried out all these steps though I keep getting the same error. How can i get a successful backup?
Diana Piloya 185 Reputation points

2026-03-12T02:32:41.62+00:00

Hello @Suchitra Suregaunkar , I have tried the recommended approach and excluded the suggested files though I am still getting this error.
Suchitra Suregaunkar 9,270 Reputation points Microsoft External Staff Moderator

2026-03-12T18:14:10+00:00

Hello @Diana Piloya

Thanks for the update, we will look into it and will keep you posted further updates.

Answer 1

Deleted

This answer has been deleted due to a violation of our Code of Conduct. The answer was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.

Comments have been turned off. Learn more

Share via

Unable to backup with MARS agent due to error

1 answer

Your answer