Veeam and Vmware 6.x CBT problems.

VMware 6.0 has a bug with CBT ( and VMware has released patch that fixes this bug.

However, installation of this fix is not the only action that should be performed to get consistent backups with Veeam or any other backup software. 

CBT reset is mandatory for the VMs, and you could do it with help of Powershell script provided by this KB article:

If you do not want to install the patch, CBT should be disabled to avoid any possible issues.

For the Veeam upgrade to version 8 update 3 - it is highly advisable not only in terms of compatibility, but also ij terms of number of varuios fixes and improvements, coming with the upgrade.

We had no issue with disabling CBT other then increased time needed for the backups, therefore I confirm that performance is the only one thing affected with CBT disabled.