- Veeam Support Knowledge Base
- Zlib decompression error: [-3] | Failed to decompress LZ4 block
Zlib decompression error: [-3] | Failed to decompress LZ4 block
| KB ID: | 1795 |
| Product: | Veeam Backup & Replication | 6.5 | 7.0 | 8.0 | 9.0 | 9.5 | 10 | 11 | 12 | 12.1 | 12.2 | 12.3 | 12.3.1 | 12.3.2 | 13 | 13.1 |
| Published: | 2013-07-29 |
| Last Modified: | 2025-03-17 |
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Challenge
A Backup Job or Restore fails with either of the following errors:
Zlib decompression error: [-3].
or
Failed to decompress LZ4 block:
Cause
When the software reads from a an existing restore point it performs error detection using Cyclic Redundancy Checks (CRC) to validate the data. The error messages list in this article occur when a CRC fails. The error indicates that one or more blocks in the restore point are corrupted.
Solution
Restoring Missing Production Data
If the failing restore was being performed to restore missing production data, please create a Veeam Support Case. Veeam Support has tools that may be able to recover data from a restore point if it is not fully damaged.
Error During Restore
- If The 3-2-1-1-0 Rule best practice was followed, and there are multiple copies of the restore point, try using a different copy.
- If other restore points are available, try restoring from an older full backup or an incremental associated with an older full.
- If a full VM restore was attempted when the error occurred, the corrupted blocks might only affect blocks that prevent the full VM restore, but a Guest OS File Recovery may still be possible.
Error During Backup
- Try forcing the Backup Job to run an Active Full backup. The Active Full will bypass the need to read data from previous backup files. (This will not repair the broken the restore point, it simply forces the job to start a new backup chain a resume protection.)
More Information
- Veeam Backup & Replication's Data Movers use network traffic verification when transferring data between proxies and repositories to detect possible corruption. Therefore, decompression errors are unlikely to be caused by a malfunctioning NIC, router, or other network device if the repository server uses a local disk (Windows Repository | Linux Repository).
- For Windows Repositories, the event log on the repository server may contain Disk Event 7: “The device… has a bad block.” If so, consider running CHKDSK /F or /R to scan for and attempt to repair bad blocks. If additional bad block events occur after running CHKDSK, check the SMART status and consider replacing the disk.
- When backing up to a CIFS share, NFS share, or iSCSI volume, malfunctioning network hardware may cause corrupted backup files because Veeam's network traffic verification cannot verify data sent to those destinations.
- Enabling Storage-level corruption guard will cause the backup/backup copy job to perform automatic checks to proactively detect CRC failures due to corrupted backup files.
- If disk failure is a suspected cause of restore point corruption when using a Network Attached Storage device, contact the storage vendor to determine what diagnostics are available.
What is the 3-2-1-1-0 backup rule?
If this KB article did not resolve your issue or you need further assistance with Veeam software, please create a Veeam Support Case.
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