Replication job fails with "Cannot replicate disk because its capacity was reduced"

KB ID: 4232
Product: Veeam Backup & Replication
Published: 2021-11-01
Last Modified: 2021-11-01
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Challenge

After a VM's disks have been resized to be smaller, the Replication job within Veeam Backup & Replication fails with the following error:
Processing <vmname> Error: Cannot replicate disk [Datastore] vmfolder/vmname.vmdk because its capacity was reduced  
Cannot replicate disk because its capacity was reduced

Cause

This error occurs when Veeam Backup & Replication detects that the VM being replicated has had one of its disk sizes reduced, or a disk was swapped for a smaller one. The job fails because Veeam is unable to make the corresponding disk on the replica smaller to match.

Solution

You should only perform the steps documented in this solution section if you are sure that the VM being replicated has had its disk size changed. If you are unsure, contact Veeam Support to assist you in reviewing the situation to ensure there is not a deeper environmental issue, such as reference ID mismatch.

The steps below will guide you in removing the mismatched disk from the replica, thereby allowing the Replication job to recreate the disk.

Note:

  • This process will result in all restore points being removed from the replica.
  • Follow each step very closely, as these actions involve editing virtual machines and deleting disks.
  1. Note the name of the VM and the disk mentioned in the error.
Note the VM and the disk path shown in the error
  1. Edit the VM being replicated, and identify which SCSI node is assigned to the disk in the error. Cancel out of editing the VM, making no changes.
Identify SCSI node on production machine
  1. Locate the replica, and Delete All Snapshots on the replica
Remove all snapshots from the replica

The following steps involve deleting the mismatched disk from the replica. Make sure you are editing the correct VM.

  1. Edit the Replica
  2. Find the disk attached to the SCSI node identified in Step 2.
  3. Remove it using the ( X ) for the Hard disk entry.
  4. Check the box for "Delete files from datastore"
  5. Click OK to complete the process.
Identify the disk with the same SCSI node and remove it from the replica
Delete Disk From Datastore
  1. Retry the replication job containing the VM. The job will detect that all restore points have been removed and begin creating a new restore point. The disk that was removed will be recreated in full.

More information

If the source VM's disks were not altered, and this error is unexpected, this error may also be caused by:

  1. The Source VM has been mapped to the wrong replica.
  2. The disks of the source VM have had their SCSI node changed.
  3. The unique reference ID of the source VM or replica has changed, causing Veeam to interact with the wrong VM.
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