For people on ESXi 6.0 and using CommVault snaps:
Issue
VMware has identified an issue in a VMware CBT API call that can affect backups for virtual machines hosted on ESXi 6.0. The API call can return incorrect changed sectors, causing incomplete incremental backups.
The VMware ESXi engineering team is working on a fix which is slated for ESXi 6.0 Update 2. There is no current ETA on its availability. In the interim, VMware is currently suggesting to downgrade to ESX 5.5 and VM hardware version 10 as a workaround. Customers may also opt to shutdown VMs before doing an incremental backup or run full backups.
For more information, see the VMware KB article
Backups with Changed Block Tracking can return incorrect changed sectors in ESXi 6.0 (2136854) and
VDDK 6 release notes.
[h=3]For additional information, see the Commvault Books Online article
VMware CBT Issue[/h]Additionally, there is no detection criteria for which VMs have been affected.