Backup job fails with “The request is not supported. Failed to duplicate extent” message.

A backup job targetted at an ReFS based repository fails with “The request is not supported. Failed to duplicate extent"

Examples:

Agent: Failed to process method {Transform.CompileFIB}: The request is not supported.
Failed to duplicate extent. Target file: <path>vbk, Source file: <path>vib, TgtOffset: xx, SrcOffset: yy, DataSize: zz

Error: Agent: Failed to process method {Transform.Patch}: The request is not supported.
Failed to duplicate extent. Target file: <path>vbk, Source file: <path>vib, TgtOffset: xx, SrcOffset: yy, DataSize: zz

Full backup file merge failed Error: Agent: Failed to process method {Transform.Patch}: The request is not supported.
Failed to duplicate extent. Target file: <path>vbk, Source file: <path>vib, TgtOffset: xx, SrcOffset: yy, DataSize: zz

This error can occur when there is a discrepancy between the ReFS cluster size that Veeam Backup & Replication (VBR) recorded during repository creation and the actual cluster size. For example, if the ReFS volume was initially formatted with a 4K cluster size when the repository was created within VBR, and then the ReFS volume was subsequently reformatted to a 64K cluster size, VBR would still assume the ReFS volume was formatted with a 4K cluster size. This incongruity between the last known cluster size and the actual cluster size causes Synthetic Full creation and Forever-Forward Incremental retention merges to fail.

To resolve this issue, you can force Veeam Backup & Replication to recognize the change in cluster size by following these steps:

1. Identify the repository associated with the failing job.
2. Edit that repository.
3. Click Finish, and an infrastructure item update will occur.
4. After completing these steps, rerun the job.