Incremental Agentless Backups Always Transfer All Blocks

Summary

Incremental agentless backups always transfers all blocks, not only incremental changes as expected.

Symptoms

The VM had one or more snapshots before DPX enables CBT for the backup and resides on a VMFS datastore.

After removing existing VMware snapshots, agentless backups still transfer all data on the disk and not changed blocks as expected.

Resolution

In order for CBT incrementals to work correctly, reset the CBT flags on the disks being backed up:

1. Right-click the VM, click Edit settings, click the Options tab, and select Configuration Parameters.
2. Set the ctkEnabled value to false.
3. Set the scsi0:x.ctkEnabled value to false for each disk of the VM in question.
4. Open the source folder and remove any -CTK.VMDK files.
5. Power on the VM.
6. Power off the VM again. Re-enable the CTK values to true.
7. Power on the VM.

After this, DPX starts the first backup with a base, however, subsequent backups are incrementals.