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Veeam Legacy Backup Chain Format Blocks the Upgrade

Field Detail
Audience T3
Version 1.0
Last Updated October 2026
Applies To BDRs upgrading from Veeam 12.x to 13.1.1.18
Source HALO 1179664

Signal

The upgrade run halts at the gate with LegacyChainFormat - N legacy-format backup(s) of M, and nothing is installed.

Cause

Veeam 13 does not support per-job (legacy) backup chains: one shared metadata file for every machine in the job. It needs per-machine chains. The upgrade gate checks each backup's IsMetaExist flag; True means a legacy chain.

Removing the backup on its own doesn't fix it. If the repository is still set to per-job files, the job's next run writes a new legacy chain. The repository setting has to change first. This was converted on 12 BDRs during the v13 upgrade.

Before you start

  • Check free space. Step 4 writes a fresh full backup. The repository needs room for a complete full on top of what it already holds.
  • The old restore points stay on disk after step 3, and can be re-imported. Nothing is deleted until you choose to in step 7.

Procedure

  1. Switch the repository to per-machine files. In the Veeam console: Backup Infrastructure → Backup Repositories → <repository> → Edit → Repository → Advanced, and tick Use per-machine backup files. Or in PowerShell (pwsh on 13.x): 
    Set-VBRBackupRepository -Repository (Get-VBRBackupRepository -Name '<repository>') -UsePerVMFile
  2. Stop the job if it's running.
  3. Remove the legacy backup from the configuration — not from disk. In the console: Backups → Disk, right-click the backup → Remove from configuration. The files stay where they are.
  4. Start the job. It writes a new per-machine chain, beginning with a full.
  5. Confirm the new chain is per-machine: 
    & pwsh -NoProfile -Command { Import-Module Veeam.Backup.PowerShell -DisableNameChecking -WarningAction SilentlyContinue; Get-VBRBackup | Select-Object Name, IsMetaExist }
    Every backup should read IsMetaExist : False.
  6. Re-run Veeam v13 Upgrade. The gate passes.
  7. Reclaim the space once the new chain has completed and been verified. The old chain's folder is now orphaned — Veeam no longer tracks it — and can be deleted. On one BDR it held 3.47 TB.

Rollback

Until step 7, the old chain is intact on disk. To restore from it, use Backups → Import Backup in the console and point it at the old folder's metadata file.

If it comes back

If the gate reports a legacy chain again after conversion, check the repository setting again: the job may be writing to a second repository that still uses per-job files, or the setting may have been reverted. Then repeat from step 2.

Version Date Author Change
1.0 October 2026 Z. Boogher Initial release from the legacy-chain conversions during the v13 upgrade (HALO 1179664).
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