Unknown Change Tracking Version

Product version: 10.0

Last modified: 30 June 2020


The VMware backup/recovery/replication job fails with the following error:

Backup/Replication/Recovery of the "X" VM has failed.

Unknown change tracking version.


In vSphere v7.0, the disks greater than 256GB require change tracking (CTK) v2.0 which is not supported by older vSphere versions. Therefore, when you use the HotAdd transport mode to save a VM of virtual hardware version (VHV) 17 with enabled CBT and a large virtual disk, the backup/replication/recovery job fails due to the following reasons:

  • The VHV of the backed up VM is 17 or higher.

  • The saved disk size is greater than 256GB.

  • The CBT was reinitialized on a 7.0 ESXi host. 


To solve the problem, do one of the following:

  •  Disable CBT on the target VM to avoid the CTK problem (not recommended because full backups will ensue after that).

  •  Migrate the backup proxy VM to a host running ESXi 7.0 using vMotion.