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- Backup Copy or Replication job using WAN accelerators fails with “Source WAN accelerator error: Failed to decompress LZ4 block”
Backup Copy or Replication job using WAN accelerators fails with “Source WAN accelerator error: Failed to decompress LZ4 block”
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Challenge
A Backup Copy or Replication job that utilizes WAN Accelerator fails with any of the following errors:
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Error: Source WAN accelerator error: Failed to decompress LZ4 block: Bad crc
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Error: Source WAN accelerator error: Failed to decompress LZ4 block: Incorrect decompression result or length
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Error: Source WAN accelerator error: Client error: Zlib decompression error: [-3].
Cause
Solution
Issue Isolation
To begin the investigation, isolate whether the issue is related to the WAN Accelerator Cache or the Restore Points.
- Edit the job that is failing.
- Switch to the Data Transfer section of the job configuration.
- Change the job to use 'Direct' instead of 'Through built-in WAN accelerators'.
- Run the Job, and observe the outcome.
Job Succeeds in Direct Data Transfer Mode
If the job functions without error when it has been configured to not the WAN Accelerators, the issue likely lies in the WAN Accelerator Cache.
- Clear the WAN Accelerator's Cache
- (Optional) Manually Populate the WAN Accelerator Cache
- Configure the Job to use the WAN Accelerator Cache
- Modify the Job again.
- Switch to the Data Transfer section of the job configuration.
- Change the job to use 'Direct' instead of 'Through built-in WAN accelerators'.
- Run the Job, and observe the outcome.
Job Fails in Direct Data Transfer Mode
If, after configuring the job to not use the WAN Accelerator, the error persists, it likely indicates an issue with the backup files being unable to recompress.
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Run an active full backup on the source job. This will recreate the backup file entirely from the source data. Once completed, re-run the backup copy job to pull data from the new restore point.
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If the error continues, trigger an active full backup on the backup copy job. Veeam will read the data from the new backup file, bypassing all previous backup files on both the source and target repositories. This will help isolate the problem from any previous backup file corruption.
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If the error still persists, begin investigating the underlying storage. At this stage, you will have generated new source and target backup files and ruled out the WAN accelerator components. Although uncommon, it is likely that corruption on one of the storage volumes is causing consistency errors.
More Information
The Windows event log on the repository server may contain Disk Event 7: “The device… has a bad block.” If so, run CHKDSK /F or /R. A small number of bad blocks are normal on most storage devices. If additional bad block events occur after running CHKDSK, check the SMART status and consider replacing the disk. If using a Network Attached Storage device, contact your storage vendor to determine what diagnostics are available.
For more information, review: Veeam KB1795.
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