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How to Manually Repair a VMware Replica created by Veeam

KB ID: 1773
Product: Veeam Backup & Replication | 12 | 12.1 | 12.2 | 12.3 | 12.3.1 | 12.3.2
Published: 2013-06-20
Last Modified: 2025-08-28
Languages: JP
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The actions documented in this article should never be performed on a production virtual machine (VM), as they intentionally lead to the VM losing data. That data loss is only acceptable with a Veeam replica, because the replica will be repaired and brought back up-to-date when the next replication job run.
Article Applicability

This article is not intended for use with:

Purpose

This article explains how to manually revert a replica to its base disks, allow it to be remapped to a replication job and used as a seed when the replica's snapshot files have become corrupt.

The following are error messages that may prompt the use of this KB article:

  • A replication job may fail with a message such as: 
    Unable to repair replica VM.
  • When the replication job fails to create a snapshot on the replica with: 
    File or folder already exists.
    This occurs most often when a loose file is named like a snapshot but is not associated with the replica (e.g., DC01-0000001.VMDK), is in the folder with the replica files. When VMware creates the first snapshot on the replica it can’t because the file it was going to create has the same name as the aforementioned loose file.
  • Replication job fails with: 
    Invalid Snapshot Configuration
    Verify that the error is coming from the replica by checking the replica's Tasks & Events.
  • Replication job fails with: 
    CID mismatch error: The parent virtual disk has been modified since the child was created
    Verify that the error is coming from the replica by checking the replica's Tasks & Events.

Solution

Please be aware that as an alternative to performing the steps below, you may first attempt to clone the faulty replica within VMware; if it succeeds, map the Replication job to the clone of the replica.

Before Beginning

  1. Stop all other replication jobs to the destination location of the replica facing the issue.
  2. Manually check each target side proxy for stuck replica hotadded disks (VMDK disks belonging to the replica that remain attached to the target proxy after the job is completed). See KB1775 for details.
    Consider switching the target proxies to Network Transport mode to prevent stuck hotadded disks if it becomes a recurring issue.

Gather Information About the Replica

The following actions are performed with the replica VM using a vSphere Client.

  1. Edit the Replica in vSphere Client.
  2. Note which disk files correlate to each SCSI ID.
    Example: 
    [supstg02] TestVM_replica\TestVM_1-000001.vmdk on SCSI0:0
[supstg02] TestVM_replica\TestVM-000001.vmdk on SCSI0:1
[supstg02] TestVM_replica\TestVM_2-000001.vmdk on SCSI0:2
screenshot showing VM settings with disks 1 and 2 expanded to show their disk path and associated scsi ID
  1. Switch to the VM Options tab and take note of the VM Config File location.
    You'll need to know this in the future step when you have to edit that config file.
Screenshto of VM configuration location in VM Options tab of VM settings.

Clean Up Snapshots on the Replica

The following actions are performed with the replica VM using a vSphere Client.

  1. Remove as many snapshots as the vSphere Client will allow:
    1. Open the Snapshot Manager.
    2. Select the oldest snapshot.
    3. Delete the oldest snapshot.
    4. Repeat the two steps above (b+c) to merge as much new data into the base disks as possible.

      At some point, though, there will be a snapshot that cannot be removed.
  2. If any snapshots are left in the snapshot manager, try using the Delete All option in the snapshot manager.
    This will likely fail, but it's worth a try to get as much recent data as possible merged into the base VMDKs.
  3. Use the consolidate function to consolidate any orphaned snapshots.

    Note:     It is expected that these steps will fail at some point. When you receive a failure, move on to the next step.

Remove the Replica from Veeam Backup & Replication

  1. Within the Veeam Backup & Replication Console, under Replicas, find the replica to be repaired and right-click it.
  2. From the context menu, select Remove from configuration.

    Note: After you use the Remove from configuration function, the VM will be removed from the Replication job. You'll need to manually re-add the VM to the replication job during the final steps of this procedure.

Remove VM from Inventory, Modify Replica VMX, and Re-register Replica

Due to changes starting in vSphere 7, it is no longer possible to remove a snapshot disk from a VM. Therefore, the only option is to directly modify the VM configuration file (.vmx) and re-register the VM.

  1. Using a vSphere Client, right-click on the Replica and select Remove from inventory.
  2. Edit the replica's VM configuration file (.vmx) to update the disk filename to point at the replica's base VMDK file.

    Notes:
    • In most cases, this is as simple as removing the -00000# portion from the filename.
      Example: scsi0:0.fileName = "TestVM_1-000001.vmdk" becomes scsi0:0.fileName = "TestVM_1.vmdk"
    • Remember to match the SCSI ID to the correct files based on Step 4.
Screenshot of the files view within the Veeam Backup & Replication console with the vcenter expanded to select the datastore where the replica VM's folder is and the VMX file right clicked and the Edit option in the context menu selected.
Screenshot of text editor with Replica VMX file open. Highlight is the line for scsi0:1.filename with the -00001 portion of the recorded filename highlighted indicate that it's the part that needs to be removed.
Highlighted is the part that needs to be removed to return the configuration to pointing at the base disk.
  1. After editing the scsiX:Y.filename lines in the Replica's VMX file, save it.
  2. Open the vSphere client and navigate to the VMX location and register the replica VM.

Datastore Cleanup

  1. Using the datastore browser, go to the folder of the replica.
  2. Most likely, there will be many files; keep in mind that the only files that are required are:
    • VMX — Virtual machine configuration file
    • VMXF — Optional additional virtual machine configuration files
    • NVRAM — Virtual machine BIOS or EFI configuration
    • VMDK — Virtual machine data disk (one base VMDK per disk)
      Note: Technically, the .vmdk file is a descriptor file, and the actual data contents are stored in a -flat.vmdk (base disk) or -delta.vmdk (snapshot) file. These flat and delta files remain hidden as long as there is a matching .vmdk file in the same folder. Snapshot .vmdk files can typically be identified by their names, which include a hyphen and six digits before the .vmdk extension (e.g., TestVM-000001.vmdk).

    So, for example, here is a folder pre-cleanup post repair.

screenshot of the datastore folder with various files associated with the replica VM
The following files can be safely removed:
screenshot of the same datastore folder with every file EXCEPT the VMX, base VMDK, and NVRAM selected. Leaving the VMX, VMXF, NVRAM, and the VMDK for each disk.
Removing the associated snapshot files that are no longer needed.
Screenshot of datastore folder with only the VMX, VMDK, and NVRAM files

Test the replica

  1. Create a snapshot on the replica.
  2. Remove the snapshot.
  3. If no error occurs, re-add the VM to the replication job and map the replica.
  4. See if the job runs successfully.
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